feat(gmw): moderation explainability + semantic message search

- Persist structured verdict (flags/severity/confidence/evidence) on
  moderation_actions so the public web can show WHY a message was moderated.
- Add a persistent Qdrant archive collection (gmw_message_archive); embed
  every captured message at capture time (fire-and-forget, best-effort).
- Public semantic search over the archive (backend oRPC + FE toggle on the
  messages view). Both features are read-only/public and fully automatic.

Migration: 0015_add_moderation_explainability.sql

services/frontend/src/hooks/use-messages.ts

@@ -2,7 +2,12 @@ import { useEffect, useState } from "react";
 import useSWR, { useSWRConfig } from "swr";
 import { useAction } from "@/hooks/use-action";
 import { messagesApi, voiceApi } from "@/lib/api";
-import type { AttachmentRecord, Channel, MessageRecord } from "@/lib/types";
+import type {
+  AttachmentRecord,
+  Channel,
+  MessageRecord,
+  SemanticSearchResult,
+} from "@/lib/types";
 import type { WsHook } from "@/lib/ws-hook";
 
 // ── Query keys factory ───────────────────────────
@@ -177,6 +182,21 @@ export function useMessageSearch(query: string, enabled: boolean) {
   );
 }
 
+// ── Semantic Search (public archive, Qdrant) ──────
+
+export function useSemanticSearch(query: string, enabled: boolean) {
+  return useSWR<SemanticSearchResult[]>(
+    enabled && query.trim().length >= 2
+      ? ["semantic-search", query.trim()]
+      : null,
+    async () => {
+      const res = await messagesApi.semanticSearch(query.trim(), 10);
+      return res.results;
+    },
+    { keepPreviousData: true },
+  );
+}
+
 // ── WS sync helpers ──────────────────────────────
 
 export function useMessagesWsSync(ws: WsHook, guildId: string) {