feat(gmw): public features #2-#6 — live moderation feed, toxic topic trends, channel timeline, CSV export, activity heatmap

- Live Moderation Feed: gateway publishes discord:moderation:action (Redis) → backend WS emits moderation_action → public web shows realtime stream.
- Toxic Topic Trends: backend moderation.trends aggregates categories/severity/action_type (read-only) → SVG bar + donut.
- Channel Timeline: messages view gets Feed/Timeline toggle with date-grouped separators.
- CSV Export: client-side downloadCsv for moderation actions (no backend write scope).
- Activity Heatmap: backend messages.activity (per-hour volume by channel) → pure-SVG grid.

User reputation deliberately excluded — no such feature exists in the codebase.
All read-only / public-facing / fully automatic per project rules.

services/frontend/src/lib/api/messages.ts

@@ -1,6 +1,7 @@
 import { orpc } from "@/lib/orpc/client";
 import type {
   AttachmentRecord,
+  MessageActivityBucket,
   MessageRecord,
   SemanticSearchResult,
 } from "@/lib/types";
@@ -73,4 +74,10 @@ export const messagesApi = {
       results: SemanticSearchResult[];
       nextCursor: null;
     }>,
+
+  // Public, read-only activity heatmap data (per-hour volume by channel).
+  getActivity: (days = 30) =>
+    orpc.messages.activity({ days }) as unknown as Promise<
+      MessageActivityBucket[]
+    >,
 };

services/frontend/src/lib/api/moderation.ts

@@ -1,5 +1,9 @@
 import { orpc } from "@/lib/orpc/client";
-import type { ModerationStats, PaginatedModerationActions } from "@/lib/types";
+import type {
+  ModerationStats,
+  ModerationTrends,
+  PaginatedModerationActions,
+} from "@/lib/types";
 
 export const moderationApi = {
   getStats: () =>
@@ -17,4 +21,7 @@ export const moderationApi = {
       actionType,
       cursor,
     }) as unknown as Promise<PaginatedModerationActions>,
+
+  getTrends: (days = 30) =>
+    orpc.moderation.trends({ days }) as unknown as Promise<ModerationTrends>,
 };

services/frontend/src/lib/csv.ts

@@ -0,0 +1,32 @@
+/** Client-side CSV export. Pure browser — no backend, no write scope. */
+export function toCsv(rows: Record<string, unknown>[]): string {
+  if (rows.length === 0) return "";
+  const headers = Array.from(
+    rows.reduce<Set<string>>((s, r) => {
+      Object.keys(r).forEach((k) => s.add(k));
+      return s;
+    }, new Set()),
+  );
+  const esc = (v: unknown): string => {
+    if (v == null) return "";
+    const s = typeof v === "object" ? JSON.stringify(v) : String(v);
+    return /[",\n]/.test(s) ? `"${s.replace(/"/g, '""')}"` : s;
+  };
+  const head = headers.map(esc).join(",");
+  const body = rows
+    .map((r) => headers.map((h) => esc(r[h])).join(","))
+    .join("\n");
+  return `${head}\n${body}`;
+}
+
+export function downloadCsv(filename: string, rows: Record<string, unknown>[]) {
+  const csv = toCsv(rows);
+  if (!csv) return;
+  const blob = new Blob([csv], { type: "text/csv;charset=utf-8;" });
+  const url = URL.createObjectURL(blob);
+  const a = document.createElement("a");
+  a.href = url;
+  a.download = filename;
+  a.click();
+  URL.revokeObjectURL(url);
+}

services/frontend/src/lib/types/message.ts

@@ -173,6 +173,12 @@ export interface SemanticSearchResult {
   created_at: number;
 }
 
+export interface MessageActivityBucket {
+  channelId: string;
+  hour: number;
+  count: number;
+}
+
 export interface SemanticSearchResponse {
   results: SemanticSearchResult[];
   nextCursor: null;

services/frontend/src/lib/types/moderation.ts

@@ -44,3 +44,9 @@ export interface PaginatedModerationActions {
   data: ModerationAction[];
   nextCursor: string | null;
 }
+
+export interface ModerationTrends {
+  categories: { name: string; count: number }[];
+  severities: { level: string; count: number }[];
+  actions: { type: string; count: number }[];
+}

services/frontend/src/lib/ws/types.ts

@@ -2,6 +2,7 @@ import type {
   ActiveSpeaker,
   MediaState,
   MessageRecord,
+  ModerationAction,
   VoiceRecording,
 } from "@/lib/types";
 
@@ -68,6 +69,8 @@ export interface WsEventMap {
   presence_updated: unknown;
   guild_member_added: unknown;
   guild_member_removed: unknown;
+  /** Live moderation action broadcast (gateway → Redis → backend → WS). */
+  moderation_action: ModerationAction;
   media_state: MediaState;
   user_state: unknown;
   ui_state: unknown;