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/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;