feat: integrate Matrix chat (Option 2 - credentials stored in Supabase)

- Add matrix-js-sdk, marked, highlight.js, twemoji, @tanstack/svelte-virtual deps
- Copy Matrix core layer: /matrix/, /stores/matrix.ts, /cache/, /services/
- Copy Matrix components: matrix/, message/, chat-layout/, chat-settings/
- Copy UI components: EmojiPicker, Twemoji, ImagePreviewModal, VirtualList
- Copy utils: emojiData, twemoji, twemojiGlobal
- Replace lucide-svelte with Material Symbols in SyncRecoveryBanner
- Extend Avatar with xs size and status indicator prop
- Fix ui.ts store conflict: re-export toasts from toast.svelte.ts
- Add migration 020_matrix_credentials for storing Matrix tokens per user/org
- Add /api/matrix-credentials endpoint (GET/POST/DELETE)
- Create [orgSlug]/chat page with Matrix login form + full chat UI
- Add Chat to sidebar navigation

src/lib/services/index.ts

@@ -0,0 +1,23 @@
+/**
+ * Services Barrel Export
+ * 
+ * Centralized exports for all service modules.
+ */
+
+export {
+  reactionService,
+  addReaction,
+  removeReaction,
+  toggleReaction,
+  clearPendingOperations,
+  isOperationPending,
+  hasPendingOperations,
+  pendingReactionsList,
+  categorizeReactionError,
+  isTransientError,
+  ReactionErrorType,
+  type ReactionOperation,
+  type ReactionOperationType,
+  type ReactionOperationStatus,
+  type CategorizedError,
+} from './reactions';