feat(db-hardening): Add database persistence, backups, and MinIO assets storage

Database Hardening:
- Add docker-compose.db.yml with persistent PostgreSQL volume
- Add automatic DB backups every 12h (7 days, 4 weeks, 6 months retention)
- Add MinIO S3-compatible storage for assets

Assets Migration:
- Add MinIO client (lib/assets_client.py) for upload/delete
- Update upload endpoint to use MinIO (with local fallback)
- Add migration 043_asset_urls_to_text.sql for full HTTPS URLs
- Simplify normalizeAssetUrl for S3 URLs

Recovery:
- Add seed_full_city_reset.py for emergency city recovery
- Add DB_RESTORE.md with backup restore instructions
- Add SEED_RECOVERY.md with recovery procedures
- Add INFRA_ASSETS_MINIO.md with MinIO setup guide

Task: TASK_PHASE_DATABASE_HARDENING_AND_ASSETS_MIGRATION_v1

migrations/043_asset_urls_to_text.sql

@@ -0,0 +1,33 @@
+-- 043_asset_urls_to_text.sql
+-- Migration: Change asset URL fields to text to support full HTTPS URLs from MinIO/S3
+
+-- MicroDAO logo and banner URLs
+ALTER TABLE microdao
+    ALTER COLUMN logo_url TYPE text,
+    ALTER COLUMN banner_url TYPE text;
+
+COMMENT ON COLUMN microdao.logo_url IS 'Full HTTPS URL to logo image (e.g., https://assets.daarion.space/daarion-assets/microdao/logo/...)';
+COMMENT ON COLUMN microdao.banner_url IS 'Full HTTPS URL to banner image (e.g., https://assets.daarion.space/daarion-assets/microdao/banner/...)';
+
+-- Agent avatar URLs
+ALTER TABLE agents
+    ALTER COLUMN avatar_url TYPE text;
+
+COMMENT ON COLUMN agents.avatar_url IS 'Full HTTPS URL to avatar image (e.g., https://assets.daarion.space/daarion-assets/agents/avatar/...)';
+
+-- City rooms logo and banner (if exists)
+DO $$
+BEGIN
+    IF EXISTS (SELECT 1 FROM information_schema.columns 
+               WHERE table_name = 'city_rooms' AND column_name = 'logo_url') THEN
+        ALTER TABLE city_rooms ALTER COLUMN logo_url TYPE text;
+        COMMENT ON COLUMN city_rooms.logo_url IS 'Full HTTPS URL to room logo image';
+    END IF;
+    
+    IF EXISTS (SELECT 1 FROM information_schema.columns 
+               WHERE table_name = 'city_rooms' AND column_name = 'banner_url') THEN
+        ALTER TABLE city_rooms ALTER COLUMN banner_url TYPE text;
+        COMMENT ON COLUMN city_rooms.banner_url IS 'Full HTTPS URL to room banner image';
+    END IF;
+END $$;
+