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/src/components/TypingIndicator.tsx

@@ -0,0 +1,33 @@
+import { useTypingStore } from '../stores/typing.ts';
+import { useAuthStore } from '../stores/auth.ts';
+
+interface TypingIndicatorProps {
+  channelId: string;
+}
+
+export function TypingIndicator({ channelId }: TypingIndicatorProps) {
+  const typingUsers = useTypingStore((state) => state.typingUsers[channelId] || []);
+  const currentUser = useAuthStore((state) => state.user);
+
+  // Filter out current user
+  const others = typingUsers.filter(u => u.userId !== currentUser?.id);
+
+  if (others.length === 0) return null;
+
+  const names = others.map(u => u.username);
+
+  let text: string;
+  if (names.length === 1) {
+    text = `<${names[0]}> is typing...`;
+  } else if (names.length === 2) {
+    text = `<${names[0]}> and <${names[1]}> are typing...`;
+  } else {
+    text = `${names.length} users are typing...`;
+  }
+
+  return (
+    <div className="px-4 py-1 text-xs text-gb-fg-f font-mono animate-pulse">
+      {text}
+    </div>
+  );
+}