fix: restore atmosphere background and add home button

atmosphere:
- restored rotating 3D atmosphere with app logos
- fetches top atproto apps from UFOs API
- displays app avatars with tooltips
- 24-hour caching for performance

navigation:
- added home button at top right corner
- positioned next to watch-live button
- provides navigation back to landing page

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

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

src/templates.rs

···
         function toggleInfo() {
             document.getElementById('infoContent').classList.toggle('expanded');
         }
+
+        // Atmosphere rendering
+        async function fetchAtmosphere() {
+            const CACHE_KEY = 'atme_atmosphere';
+            const CACHE_DURATION = 24 * 60 * 60 * 1000; // 24 hours
+
+            const cached = localStorage.getItem(CACHE_KEY);
+            if (cached) {
+                const { data, timestamp } = JSON.parse(cached);
+                if (Date.now() - timestamp < CACHE_DURATION) {
+                    return data;
+                }
+            }
+
+            try {
+                const response = await fetch('https://ufos-api.microcosm.blue/collections?order=dids-estimate&limit=50');
+                const json = await response.json();
+
+                // Group by namespace (first two segments)
+                const namespaces = {};
+                json.collections.forEach(col => {
+                    const parts = col.nsid.split('.');
+                    if (parts.length >= 2) {
+                        const ns = `${parts[0]}.${parts[1]}`;
+                        if (!namespaces[ns]) {
+                            namespaces[ns] = {
+                                namespace: ns,
+                                dids_total: 0,
+                                records_total: 0,
+                                collections: []
+                            };
+                        }
+                        namespaces[ns].dids_total += col.dids_estimate;
+                        namespaces[ns].records_total += col.creates;
+                        namespaces[ns].collections.push(col.nsid);
+                    }
+                });
+
+                const data = Object.values(namespaces).sort((a, b) => b.dids_total - a.dids_total).slice(0, 30);
+
+                localStorage.setItem(CACHE_KEY, JSON.stringify({
+                    data,
+                    timestamp: Date.now()
+                }));
+
+                return data;
+            } catch (e) {
+                console.error('Failed to fetch atmosphere data:', e);
+                return [];
+            }
+        }
+
+        async function fetchAppAvatar(namespace) {
+            const reversed = namespace.split('.').reverse().join('.');
+            const handles = [reversed, `${reversed}.bsky.social`];
+
+            for (const handle of handles) {
+                try {
+                    const didRes = await fetch(`https://public.api.bsky.app/xrpc/com.atproto.identity.resolveHandle?handle=${handle}`);
+                    if (!didRes.ok) continue;
+
+                    const { did } = await didRes.json();
+                    const profileRes = await fetch(`https://public.api.bsky.app/xrpc/app.bsky.actor.getProfile?actor=${did}`);
+                    if (!profileRes.ok) continue;
+
+                    const profile = await profileRes.json();
+                    if (profile.avatar) return profile.avatar;
+                } catch (e) {
+                    continue;
+                }
+            }
+            return null;
+        }
+
+        async function renderAtmosphere() {
+            const data = await fetchAtmosphere();
+            if (!data.length) return;
+
+            const atmosphere = document.getElementById('atmosphere');
+            const maxSize = Math.max(...data.map(d => d.dids_total));
+
+            data.forEach((app, i) => {
+                const orb = document.createElement('div');
+                orb.className = 'app-orb';
+
+                // Size based on user count (20-80px)
+                const size = 20 + (app.dids_total / maxSize) * 60;
+
+                // Position in 3D space
+                const angle = (i / data.length) * Math.PI * 2;
+                const radius = 250 + (i % 3) * 100;
+                const y = (i % 5) * 80 - 160;
+                const x = Math.cos(angle) * radius;
+                const z = Math.sin(angle) * radius;
+
+                orb.style.width = `${size}px`;
+                orb.style.height = `${size}px`;
+                orb.style.left = `calc(50% + ${x}px)`;
+                orb.style.top = `calc(50% + ${y}px)`;
+                orb.style.transform = `translateZ(${z}px) translate(-50%, -50%)`;
+                orb.style.background = `radial-gradient(circle, rgba(255,255,255,0.1), rgba(255,255,255,0.02))`;
+                orb.style.border = '1px solid rgba(255,255,255,0.1)';
+                orb.style.boxShadow = '0 0 20px rgba(255,255,255,0.1)';
+
+                // Fallback letter
+                const letter = app.namespace.split('.')[1]?.[0]?.toUpperCase() || app.namespace[0].toUpperCase();
+                orb.innerHTML = `<div class="fallback">${letter}</div>`;
+
+                // Tooltip
+                const tooltip = document.createElement('div');
+                tooltip.className = 'app-tooltip';
+                const users = app.dids_total >= 1000000
+                    ? `${(app.dids_total / 1000000).toFixed(1)}M users`
+                    : `${(app.dids_total / 1000).toFixed(0)}K users`;
+                tooltip.textContent = `${app.namespace} • ${users}`;
+                orb.appendChild(tooltip);
+
+                atmosphere.appendChild(orb);
+
+                // Fetch and apply avatar
+                fetchAppAvatar(app.namespace).then(avatarUrl => {
+                    if (avatarUrl) {
+                        orb.innerHTML = `<img src="${avatarUrl}" alt="${app.namespace}" />`;
+                        orb.appendChild(tooltip);
+                    }
+                });
+            });
+        }
+
+        renderAtmosphere();
     </script>
 </body>
 </html>