feat(glossary): persist resolved definitions in Postgres + harden live SearXNG lookups

- Add term_glossary_cache table + migration 0014: resolved definitions are
  stored permanently (definitions rarely change); misses stay ephemeral in
  Redis/LRU with 1h TTL so transient failures get retried
- Lookup flow: LRU -> Redis -> Postgres (permanent) -> live SearXNG; DB hits
  re-warm the fast caches; stale Redis miss sentinels no longer shadow DB
- Rate-limit-aware live lookups: concurrency 2 + stagger, retry once on empty
  results, strict definition filter (Wikipedia preferred, rejects
  disambiguation/ads/translate-homepages)
- Make SEARXNG_BASE_URL configurable via env (default unchanged)

services/discord-gateway/src/modules/ai-moderation/searxngSearch.ts

@@ -1,10 +1,11 @@
 import Redis from "ioredis";
 import { createChildLogger } from "@/shared/logger/index";
 import { createAbortControllerWithTimeout } from "@/shared/utils/index";
+import { config } from "../../shared/config/config.js";
 
 const log = createChildLogger("searxng-search");
 
-const SEARXNG_BASE_URL = "https://searxng.imrnes.team";
+const SEARXNG_BASE_URL = config.SEARXNG_BASE_URL;
 const MAX_RESULTS = 3;
 const TIMEOUT_MS = 8000;
 const CACHE_TTL = 86400; // 24 hours