Revert "feat: migrate frontend to Astro + expand AI moderation + backend admin/runtime config"

This reverts commit d59b59a7a7.

services/discord-gateway/drizzle/migrations/0012_light_prism.sql

@@ -1 +0,0 @@
-CREATE INDEX IF NOT EXISTS "idx_messages_guild_ai_status_analyzed" ON "messages" USING btree ("guild_id","ai_status","ai_analyzed_at","id");--> statement-breakpoint

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

@@ -85,13 +85,6 @@
       "when": 1781388000000,
       "tag": "0011_add_voice_transcription",
       "breakpoints": true
-    },
-    {
-      "idx": 12,
-      "version": "7",
-      "when": 1781672400000,
-      "tag": "0012_light_prism",
-      "breakpoints": true
     }
   ]
 }