feat(db): add migrations for user reputation and channel culture tables

Adds new database schema migrations to support the implementation of
user reputation tracking and channel-specific culture context.

- Creates migration `0005_large_squadron_sinister.sql` containing
  `user_reputations` and `channel_cultures` tables.
- Updates Drizzle migration journal to include the new migration step.
- Adds `fix_prompt.py` utility for managing prompt adjustments.

services/discord-gateway/drizzle/migrations/meta/_journal.json

@@ -36,6 +36,13 @@
       "when": 1780418800000,
       "tag": "0004_drop_unused_ai_columns",
       "breakpoints": true
+    },
+    {
+      "idx": 5,
+      "version": "7",
+      "when": 1780657801437,
+      "tag": "0005_large_squadron_sinister",
+      "breakpoints": true
     }
   ]
 }