fix: backend and discord-gateway improvements

- Update shared database schema
- Add shared utils
- Refactor backend middleware, auth routes, and dashboard repository
- Improve media analysis client with better error handling
- Fix searxng search URL construction
- Update URL fetcher for robustness

Co-authored-by: workflow agents

packages/shared/src/database/schema.ts

@@ -83,6 +83,12 @@ export const pgMessagesTable = pgTable(
       table.created_at,
       table.id,
     ),
+    guildAiStatusAnalyzedIdx: pgIndex("idx_messages_guild_ai_status_analyzed").on(
+      table.guild_id,
+      table.ai_status,
+      table.ai_analyzed_at,
+      table.id,
+    ),
     guildCreatedDeletedIdx: pgIndex("idx_messages_guild_created_deleted").on(
       table.guild_id,
       table.created_at,