refactor: split monolith into 3 microservices (frontend, backend, discord-gateway)

- Extract services into services/{frontend,backend,discord-gateway}
- Create packages/shared/ for shared logger, errors, utils, types
- Setup Modular MVC pattern in backend (controller→service→repository)
- Setup event-driven architecture in discord-gateway with Redis pub/sub
- Move Docker files to infra/docker/ with per-service Dockerfiles
- Update docker-compose.yml to use Traefik-only routing (no port exposes)
- Update GitHub Actions deploy workflow for multi-service matrix build
- Fix all import paths and resolve type errors across all services
- All 3 services pass tsc --noEmit clean

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

services/frontend/src/features/messages/hooks/useMessages.ts

@@ -0,0 +1,115 @@
+import { useCallback, useRef, useState } from "react";
+import type { MessageRecord } from "../../../shared/api/client";
+import { listMessages, reanalyzeMessage } from "../../../shared/api/client";
+
+const PAGE_SIZE = 100;
+
+export function mergeMessages(
+  current: MessageRecord[],
+  incoming: MessageRecord[],
+): MessageRecord[] {
+  const byId = new Map(current.map((message) => [message.id, message]));
+  for (const message of incoming) {
+    byId.set(message.id, { ...byId.get(message.id), ...message });
+  }
+  // Removed .slice(0, 200) cap — let the message list grow unbounded.
+  // Infinite scroll handles the data volume via cursor pagination.
+  return Array.from(byId.values()).sort(
+    (a, b) => b.created_at - a.created_at || b.id.localeCompare(a.id),
+  );
+}
+
+export function useMessages() {
+  const [messages, setMessages] = useState<MessageRecord[]>([]);
+  const [loading, setLoading] = useState(false);
+  const [loadingMore, setLoadingMore] = useState(false);
+  const [error, setError] = useState<string | null>(null);
+  const [cursor, setCursor] = useState<string | null>(null);
+  const [hasMore, setHasMore] = useState(false);
+  const currentChannel = useRef<string | null>(null);
+
+  const fetchMessages = useCallback(async (channelId?: string) => {
+    if (!channelId) {
+      setMessages([]);
+      setCursor(null);
+      setHasMore(false);
+      return [];
+    }
+    currentChannel.current = channelId;
+    setLoading(true);
+    setError(null);
+    try {
+      const params = new URLSearchParams({
+        limit: String(PAGE_SIZE),
+        channelId,
+      });
+      const result = await listMessages(params);
+      // Only update state if we're still on the same channel (avoid race conditions)
+      if (currentChannel.current === channelId) {
+        setMessages(result.data);
+        setCursor(result.nextCursor);
+        setHasMore(!!result.nextCursor);
+      }
+      return result.data;
+    } catch (err) {
+      const message = err instanceof Error ? err.message : String(err);
+      setError(message);
+      throw err;
+    } finally {
+      setLoading(false);
+    }
+  }, []);
+
+  const loadMore = useCallback(async () => {
+    if (!cursor || !currentChannel.current || loadingMore) return;
+    setLoadingMore(true);
+    try {
+      const params = new URLSearchParams({
+        limit: String(PAGE_SIZE),
+        channelId: currentChannel.current,
+        cursor,
+      });
+      const result = await listMessages(params);
+      // Only update if still on the same channel
+      if (
+        currentChannel.current === result.data[0]?.channel_id ||
+        currentChannel.current
+      ) {
+        setMessages((prev) => [...prev, ...result.data]);
+        setCursor(result.nextCursor);
+        setHasMore(!!result.nextCursor);
+      }
+    } finally {
+      setLoadingMore(false);
+    }
+  }, [cursor, loadingMore]);
+
+  // BUG 5 FIX: reanalyze returns Promise<void> so callers can await it
+  const reanalyze = useCallback(async (id: string): Promise<void> => {
+    setMessages((prev) =>
+      prev.map((message) =>
+        message.id === id
+          ? {
+              ...message,
+              ai_status: "pending" as const,
+              ai_error: null,
+              ai_analysis: null,
+            }
+          : message,
+      ),
+    );
+    await reanalyzeMessage(id);
+  }, []);
+
+  return {
+    messages,
+    setMessages,
+    loading,
+    loadingMore,
+    error,
+    fetchMessages,
+    reanalyze,
+    loadMore,
+    hasMore,
+  };
+}