feat: add optional text messages to guestbook signatures

users can now leave an optional message when signing the guestbook. messages are displayed in handwritten font alongside the signature metadata.

- backend: added text field to visit records and signature struct
- frontend: added message input modal with 280 char limit
- docs: updated lexicon documentation with new field and credits to @thisismissem.social and @essentialrandom.bsky.social

inspired by https://github.com/FujoWebDev/lexicon-guestbook

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[e-mail]>

docs/lexicon.md

···
 {
   "$type": "app.at-me.visit",
   "timestamp": "2025-10-25T22:30:00Z",
-  "createdAt": "2025-10-25T22:30:00Z"
+  "createdAt": "2025-10-25T22:30:00Z",
+  "text": "optional message from the visitor"
 }
 ```
+
+**fields:**
+- `timestamp` (required): ISO 8601 timestamp of when the signature was created
+- `createdAt` (required): ISO 8601 timestamp of when the record was created (typically same as timestamp)
+- `text` (optional): a message left by the visitor, max 280 characters
 
 ### privacy
 
···
 - user data sovereignty (records live in user's PDS)
 - transparency (users see exactly what's being written)
 - opt-in participation (no tracking without explicit consent)
+
+### acknowledgments
+
+thanks to [@thisismissem.social](https://bsky.app/profile/thisismissem.social) for putting [lexicon-guestbook](https://github.com/FujoWebDev/lexicon-guestbook) on our radar! [@essentialrandom.bsky.social](https://bsky.app/profile/essentialrandom.bsky.social)'s work on that project - a more fully-featured implementation with per-user guestbooks, moderation, and an appview - helped inform the addition of optional text messages to our simpler global guestbook.

src/routes.rs

···
     pub handle: Option<String>,
     pub avatar: Option<String>,
     pub timestamp: String,
+    pub text: Option<String>,
 }
 
 // UFOs API response structure
···
     }
 }
 
+#[derive(Deserialize)]
+pub struct SignGuestbookRequest {
+    text: Option<String>,
+}
+
 #[post("/api/sign-guestbook")]
-pub async fn sign_guestbook(session: Session) -> HttpResponse {
+pub async fn sign_guestbook(
+    session: Session,
+    body: web::Json<SignGuestbookRequest>,
+) -> HttpResponse {
     // Check if user is logged in
     let did: Option<String> = match session.get(constants::SESSION_KEY_DID) {
         Ok(d) => d,
···
         }
     };
 
-    // Create the visit record
-    let record_json = serde_json::json!({
+    // Create the visit record with optional text
+    let mut record_json = serde_json::json!({
         "$type": constants::GUESTBOOK_COLLECTION,
         "timestamp": chrono::Utc::now().to_rfc3339(),
         "createdAt": chrono::Utc::now().to_rfc3339(),
     });
+
+    // Add text field if provided
+    if let Some(text) = &body.text {
+        if !text.trim().is_empty() {
+            record_json["text"] = serde_json::Value::String(text.clone());
+        }
+    }
 
     // Convert to Unknown type
     let record: atrium_api::types::Unknown = serde_json::from_value(record_json)
···
                         handle,
                         avatar,
                         timestamp: chrono::Utc::now().to_rfc3339(),
+                        text: body.text.clone(),
                     };
 
                     // Add at the beginning (most recent)
···
                 .as_str()
                 .unwrap_or("")
                 .to_string();
+            let text = record.record["text"].as_str().map(String::from);
             async move {
                 let (handle, avatar) = fetch_profile_info(&did).await;
                 GuestbookSignature {
···
                     handle,
                     avatar,
                     timestamp,
+                    text,
                 }
             }
         })

src/templates/app.html

···
             margin-top: clamp(1.5rem, 4vmin, 2.5rem);
         }
 
+        .guestbook-message {
+            font-family: 'Brush Script MT', cursive, 'Georgia', serif;
+            font-size: clamp(1rem, 2.3vmin, 1.25rem);
+            color: #3a2f25;
+            line-height: 1.6;
+            margin-bottom: clamp(0.5rem, 1.2vmin, 0.75rem);
+            font-style: italic;
+        }
+
+        @media (prefers-color-scheme: dark) {
+            .guestbook-message {
+                color: #d4c5a8;
+            }
+        }
+
         .guestbook-paper-signature {
             padding: clamp(1rem, 2.5vmin, 1.5rem) 0;
             border-bottom: 1px solid rgba(212, 197, 168, 0.3);

static/app.js

···
     });
 }
 
+function showMessageInputModal(onConfirm) {
+    const overlay = document.createElement('div');
+    overlay.className = 'overlay';
+    overlay.style.display = 'block';
+
+    const modal = document.createElement('div');
+    modal.className = 'info-modal';
+    modal.style.display = 'block';
+    modal.style.maxWidth = '450px';
+
+    modal.innerHTML = `
+        <h2>sign the guestbook</h2>
+        <p style="margin-bottom: 1rem; color: var(--text-light);">leave an optional message (or leave blank for just a signature)</p>
+        <textarea id="guestbookMessageInput" placeholder="share your thoughts..." style="width: 100%; min-height: 80px; padding: 0.75rem; background: var(--bg); border: 1px solid var(--border); border-radius: 4px; color: var(--text); font-family: inherit; font-size: 0.8rem; resize: vertical; margin-bottom: 1rem;" maxlength="280"></textarea>
+        <div style="display: flex; gap: 0.5rem; justify-content: flex-end;">
+            <button id="cancelMessageBtn" style="background: var(--bg);">cancel</button>
+            <button id="confirmMessageBtn" style="background: var(--surface-hover);">sign</button>
+        </div>
+    `;
+
+    document.body.appendChild(overlay);
+    document.body.appendChild(modal);
+
+    const textarea = document.getElementById('guestbookMessageInput');
+    const cancelBtn = document.getElementById('cancelMessageBtn');
+    const confirmBtn = document.getElementById('confirmMessageBtn');
+
+    const closeModal = () => {
+        modal.remove();
+        overlay.remove();
+    };
+
+    cancelBtn.addEventListener('click', closeModal);
+    overlay.addEventListener('click', closeModal);
+
+    confirmBtn.addEventListener('click', () => {
+        const text = textarea.value.trim();
+        closeModal();
+        onConfirm(text);
+    });
+
+    // Focus the textarea
+    setTimeout(() => textarea.focus(), 100);
+}
+
 function showUnsignModal() {
     const overlay = document.createElement('div');
     overlay.className = 'overlay';
···
             return;
         }
 
-        // Authenticated and viewing own page - show watch prompt, then sign
+        // Authenticated and viewing own page - show message input, then watch prompt, then sign
         if (viewingOwnPage) {
-            showWatchPrompt(async () => {
-            signGuestbookBtn.disabled = true;
-            const iconSpan = signGuestbookBtn.querySelector('.guestbook-icon');
-            const textSpan = signGuestbookBtn.querySelector('.guestbook-text');
+            showMessageInputModal(async (messageText) => {
+                showWatchPrompt(async () => {
+                signGuestbookBtn.disabled = true;
+                const iconSpan = signGuestbookBtn.querySelector('.guestbook-icon');
+                const textSpan = signGuestbookBtn.querySelector('.guestbook-text');
 
-            if (iconSpan && textSpan) {
-                const originalIcon = iconSpan.innerHTML;
-                const originalText = textSpan.textContent;
-                iconSpan.innerHTML = '<svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M21 12a9 9 0 1 1-6.219-8.56"/></svg>';
-                textSpan.textContent = 'signing...';
+                if (iconSpan && textSpan) {
+                    const originalIcon = iconSpan.innerHTML;
+                    const originalText = textSpan.textContent;
+                    iconSpan.innerHTML = '<svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M21 12a9 9 0 1 1-6.219-8.56"/></svg>';
+                    textSpan.textContent = 'signing...';
 
-                try {
-                    const response = await fetch('/api/sign-guestbook', {
-                        method: 'POST',
-                        headers: {
-                            'Content-Type': 'application/json',
+                    try {
+                        const body = {};
+                        if (messageText && messageText.trim()) {
+                            body.text = messageText.trim();
                         }
-                    });
+
+                        const response = await fetch('/api/sign-guestbook', {
+                            method: 'POST',
+                            headers: {
+                                'Content-Type': 'application/json',
+                            },
+                            body: JSON.stringify(body)
+                        });
 
                     const data = await response.json();
 
···
                     }, 2000);
                 }
             }
-        });
+                });
+            });
         }
     });
 
···
                         <span class="guestbook-did-tooltip">copied!</span>
                     </div>
                     <div class="guestbook-metadata">
+                        ${sig.text ? `
+                        <div class="guestbook-message">${sig.text}</div>
+                        ` : ''}
                         <div class="guestbook-metadata-item">
                             <span class="guestbook-metadata-label">handle:</span>
                             <span class="guestbook-metadata-value">@${handle}</span>