feat: improve guestbook UX and add POV indicator

- Update POV indicator: change "point of view:" to "point of view of" and make handle a clickable Bluesky profile link
- Fix guestbook button avatar display: always show page owner's avatar, not authenticated user's avatar
- Add dynamic guestbook sign text: shows "you already signed" when page owner has signed, "sign the guest list" otherwise
- Update authentication success toast to mention both sign and unsign actions
- Add CSS styling for clickable POV handle with hover effects

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

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

src/templates/app.html

···
             margin-left: 0.3rem;
             font-size: inherit;
             opacity: 0.9;
+            pointer-events: auto;
+            text-decoration: none;
+            color: inherit;
+            transition: opacity 0.2s ease;
+        }
+
+        .pov-handle:hover {
+            opacity: 1;
+            text-decoration: underline;
         }
 
         @media (prefers-color-scheme: dark) {
···
         <span class="watch-indicator"></span>
         <span class="watch-label">watch live</span>
     </button>
-    <div class="pov-indicator">point of view:<span class="pov-handle" id="povHandle"></span></div>
+    <div class="pov-indicator">point of view of <a class="pov-handle" id="povHandle" href="#" target="_blank" rel="noopener noreferrer"></a></div>
     <div class="guestbook-sign">sign the guest list</div>
     <div class="guestbook-buttons-container">
         <button class="view-guestbook-btn" id="viewGuestbookBtn" title="view all signatures">

static/app.js

···
         const povHandleEl = document.getElementById('povHandle');
         if (povHandleEl) {
             povHandleEl.textContent = `@${viewedHandle}`;
+            povHandleEl.href = `https://bsky.app/profile/${viewedHandle}`;
         }
 
         // Display user's avatar if available
···
     linkEl.style.display = 'none';
 
     actionEl.textContent = 'signed in successfully';
-    collectionEl.innerHTML = 'you may now sign the guestbook with your identity';
+    collectionEl.innerHTML = 'you may now sign or unsign the guestbook with your identity';
 
     toast.classList.add('visible');
     setTimeout(() => {
···
         const signatures = await response.json();
         pageOwnerHasSigned = signatures.some(sig => sig.did === did || sig.did === `at://${did}`);
         console.log('[Guestbook] Page owner signed?', pageOwnerHasSigned);
+        updateGuestbookSign();
         return pageOwnerHasSigned;
     } catch (error) {
         console.error('[Guestbook] Error checking page owner signature:', error);
         return false;
+    }
+}
+
+function updateGuestbookSign() {
+    const sign = document.querySelector('.guestbook-sign');
+    if (sign) {
+        sign.textContent = pageOwnerHasSigned ? 'you already signed' : 'sign the guest list';
     }
 }
 
···
         signGuestbookBtn.classList.add('signed');
         signGuestbookBtn.setAttribute('title', viewingOwnPage ? 'you\'ve signed the guestbook' : 'this user has signed the guestbook');
         signGuestbookBtn.disabled = false; // Allow clicking to view/unsign if own page
-    } else if (isAuthenticated) {
-        // Authenticated user - show THEIR avatar (not the page owner's)
-        if (authenticatedAvatar && avatarImg) {
-            avatarImg.src = authenticatedAvatar;
+    } else {
+        // NOT signed - ALWAYS show the page owner's avatar (viewedAvatar), regardless of auth state
+        if (viewedAvatar && avatarImg) {
+            avatarImg.src = viewedAvatar;
             avatarImg.style.display = 'block';
             iconSpan.style.display = 'none';
         } else {
···
 
         textSpan.textContent = 'sign as';
 
-        if (viewingOwnPage) {
-            // Viewing own page, authenticated, ready to sign
-            signGuestbookBtn.style.background = 'var(--surface)';
-            signGuestbookBtn.style.color = 'var(--text)';
-            signGuestbookBtn.classList.add('pulse');
-            signGuestbookBtn.setAttribute('title', 'click to sign the guestbook');
-            signGuestbookBtn.disabled = false;
+        if (isAuthenticated) {
+            if (viewingOwnPage) {
+                // Viewing own page, authenticated, ready to sign
+                signGuestbookBtn.style.background = 'var(--surface)';
+                signGuestbookBtn.style.color = 'var(--text)';
+                signGuestbookBtn.classList.add('pulse');
+                signGuestbookBtn.setAttribute('title', 'click to sign the guestbook');
+                signGuestbookBtn.disabled = false;
+            } else {
+                // Authenticated but viewing someone else's page - disabled
+                signGuestbookBtn.setAttribute('title', 'visit your own page to sign');
+                signGuestbookBtn.disabled = true;
+                signGuestbookBtn.style.opacity = '0.5';
+                signGuestbookBtn.style.cursor = 'not-allowed';
+            }
         } else {
-            // Authenticated but viewing someone else's page - disabled
-            signGuestbookBtn.setAttribute('title', 'visit your own page to sign');
-            signGuestbookBtn.disabled = true;
-            signGuestbookBtn.style.opacity = '0.5';
-            signGuestbookBtn.style.cursor = 'not-allowed';
-        }
-    } else {
-        // Not authenticated - show page owner's avatar
-        if (viewedAvatar && avatarImg) {
-            avatarImg.src = viewedAvatar;
-            avatarImg.style.display = 'block';
-            iconSpan.style.display = 'none';
-        } else {
-            // No avatar - hide both avatar and icon, just show text
-            if (avatarImg) avatarImg.style.display = 'none';
-            iconSpan.style.display = 'none';
+            // Not authenticated - allow them to try to sign as this user
+            signGuestbookBtn.setAttribute('title', `sign in as @${viewedHandle || 'user'}`);
+            signGuestbookBtn.disabled = false;
         }
-
-        textSpan.textContent = 'sign as';
-        signGuestbookBtn.setAttribute('title', `sign in as @${viewedHandle || 'user'}`);
-        signGuestbookBtn.disabled = false;
     }
 }
 
···
     modal.innerHTML = `
         <h2>confirm identity</h2>
         <p style="margin-bottom: 1rem;">are you <strong>@${suggestedHandle}</strong>?</p>
-        <p style="margin-bottom: 1rem; color: var(--text-light); font-size: 0.7rem;">only you can authenticate as this person. you'll be redirected to sign in.</p>
+        <p style="margin-bottom: 1rem; color: var(--text-light); font-size: 0.7rem;">only the owner of this identity can authenticate as @${suggestedHandle}. you'll be redirected to sign in.</p>
         <div style="display: flex; gap: 0.5rem; justify-content: flex-end;">
             <button id="cancelBtn" style="background: var(--bg);">no, cancel</button>
             <button id="confirmBtn" style="background: var(--surface-hover);">yes, that's me</button>