feat(chatbot): expand tool set to cover all server-watcher situations

The chatbot agent now has 14 tools (was 4) so it can answer about ANY
server situation from live data instead of a static snapshot:

- get_server_stats (now also returns clean count)
- get_top_channels, get_recent_activity, get_top_flagged
- search_messages (LIKE keyword search)
- get_user_messages, get_user_profile, get_user_reputation
- get_channel_culture
- get_message_detail (full AI analysis of one message)
- get_message_reviews (human moderation queue by status)
- get_voice_recordings (with transcriptions)
- get_moderation_timeline (daily flagged/warn/clean trend)
- get_corrections (AI false-positive correction history)

Security/quality:
- Every executor now uses parameterized drizzle queries (eq/like/and).
  The old code interpolated model-supplied IDs into sql.raw() — a SQL
  injection vector. Removed.
- Split static tool *definitions* into chatbot.toolDefs.ts (no DB import)
  so the LLM-facing schema can be unit-tested without loading the
  database/config layer. chatbot.tools.ts keeps only the executor.

Verified: tsc + biome clean, 40 backend tests pass (4 new covering the
tool-contract: names unique, required args declared, full situation
coverage).

Co-Authored-By: Claude Opus 5 (Nous Research)

services/backend/src/modules/chatbot/chatbot.service.ts

@@ -6,7 +6,8 @@ import type {
   SaveConversationInput,
 } from "./chatbot.repository.js";
 import { chatbotRepository } from "./chatbot.repository.js";
-import { executeTool, tools } from "./chatbot.tools.js";
+import { tools } from "./chatbot.toolDefs.js";
+import { executeTool } from "./chatbot.tools.js";
 
 const logger = createChildLogger("chatbot.service");