fix(users): drop dead user_reputations JOIN that broke Members page + audit

Root cause: gateway migration 0016 removed the per-user reputation feature
(DROP TABLE user_reputations), but the backend still LEFT JOINed
pgUserReputationsTable in dashboard listUsers/getUserDetail and the chatbot
get_user_reputation tool. Against the live DB these queries raised 42P01
(undefined_table) -> the new /users page could never load (oRPC WS error).

Fix:
- dashboard.repository.ts: remove reputation columns/join from listUsers and
  getUserDetail (data sourced only from messages + user_profiles).
- chatbot.tools.ts: get_user_reputation now returns honest 'unavailable'
  (feature removed) instead of querying the dropped table.
- chatbot.toolDefs.ts: update tool description so the LLM doesn't advertise
  a dead feature.
- frontend types/users view: drop trust_score/clean_message_streak/
  total_infractions/last_infraction_at; derive risk label from real flagged%
  and add warn_count to the inspector (real available data).

Verified: backend+frontend tsc clean, biome clean, 37 unit tests pass,
query tested against live DB (returns real members), build green.

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

@@ -152,7 +152,7 @@ export const tools: ToolDef[] = [
     function: {
       name: "get_user_reputation",
       description:
-        "Ambil skor trust, jumlah infraction, dan streak pesan bersih seorang user dari user_reputations. Untuk 'berapa trust score si A?' / riwayat pelanggaran. Butuh user_id.",
+        "Cek status skor reputasi per-user. CATATAN: fitur trust score per-user telah dihapus dari sistem — tool ini menjawab 'unavailable' dan menyarankan rasio flag vs total sebagai pengganti.",
       parameters: {
         type: "object",
         properties: {