Phase 3: Polish & PWA

Backend:
- DB: reactions table, invites table, reply_to column on messages
- gateway/events.go: added REACTION_ADD, REACTION_REMOVE events
- internal/reaction/handlers.go: reaction CRUD with WebSocket broadcast
- internal/invite/handlers.go: invite creation, info, join with code
- gateway/hub.go: presence tracking with idle detection
- gateway/client.go: idle timeout support

Frontend - Social:
- TypingIndicator: real-time 'user is typing...' display
- ReactionBar: emoji reactions on messages with counts
- EmojiPicker: searchable emoji grid for reactions
- ReplyBar: quoted reply display above messages
- MentionPopup: @mention autocomplete with user list

Frontend - PWA:
- manifest.json: PWA manifest with theme color and icons
- sw.js: service worker with cache-first strategy and push support
- stores/push.ts: push notification subscription management
- InstallPrompt: 'Add to Home Screen' banner

Frontend - Mobile:
- MobileNav: bottom nav bar for mobile (servers/channels/chat/members)
- MobileDrawer: slide-out drawer with server bar + channel list
- index.html: PWA meta tags, safe area viewport

Frontend - Polish:
- ThemeToggle: dark/light mode switch with localStorage persistence
- InviteModal: generate invite links with expiry and max uses
- JoinServer: /invite/:code join flow
- stores/typing.ts: typing indicator state management
- stores/presence.ts: real-time presence tracking
- tailwind.config.js: darkMode: 'class', light mode color tokens
- styles/index.css: light mode CSS variable overrides

web/public/sw.js

@@ -0,0 +1,96 @@
+const CACHE_NAME = 'dumpster-v1';
+const STATIC_ASSETS = [
+  '/',
+  '/index.html',
+  '/manifest.json',
+];
+
+self.addEventListener('install', (event) => {
+  event.waitUntil(
+    caches.open(CACHE_NAME).then((cache) => {
+      return cache.addAll(STATIC_ASSETS);
+    })
+  );
+  self.skipWaiting();
+});
+
+self.addEventListener('activate', (event) => {
+  event.waitUntil(
+    caches.keys().then((cacheNames) => {
+      return Promise.all(
+        cacheNames
+          .filter((name) => name !== CACHE_NAME)
+          .map((name) => caches.delete(name))
+      );
+    })
+  );
+  self.clients.claim();
+});
+
+self.addEventListener('fetch', (event) => {
+  // Skip non-GET requests
+  if (event.request.method !== 'GET') return;
+
+  // Skip API requests
+  if (event.request.url.includes('/api/')) return;
+
+  // Skip WebSocket
+  if (event.request.url.includes('/ws')) return;
+
+  event.respondWith(
+    caches.match(event.request).then((cached) => {
+      // Return cached version, fetch new one in background
+      const fetchPromise = fetch(event.request).then((response) => {
+        // Only cache successful responses
+        if (response.ok) {
+          const clone = response.clone();
+          caches.open(CACHE_NAME).then((cache) => {
+            cache.put(event.request, clone);
+          });
+        }
+        return response;
+      }).catch(() => {
+        // Return cached if fetch fails
+        return cached;
+      });
+
+      return cached || fetchPromise;
+    })
+  );
+});
+
+self.addEventListener('push', (event) => {
+  if (!event.data) return;
+
+  const data = event.data.json();
+  const options = {
+    body: data.body,
+    icon: '/icons/icon-192.png',
+    badge: '/icons/badge.png',
+    vibrate: [100, 50, 100],
+    data: {
+      url: data.url || '/',
+    },
+  };
+
+  event.waitUntil(
+    self.registration.showNotification(data.title || 'Dumpster', options)
+  );
+});
+
+self.addEventListener('notificationclick', (event) => {
+  event.notification.close();
+
+  event.waitUntil(
+    clients.matchAll({ type: 'window', includeUncontrolled: true }).then((clientList) => {
+      // Focus existing window if available
+      for (const client of clientList) {
+        if (client.url.includes(event.notification.data.url) && 'focus' in client) {
+          return client.focus();
+        }
+      }
+      // Otherwise open new window
+      return clients.openWindow(event.notification.data.url);
+    })
+  );
+});