feat(scripts): add database query helpers for development

Add dbquery.py for MariaDB and sqlitequery.py for SQLite databases
in MCP service containers. Both scripts wrap docker compose exec to
simplify database inspection during development.

- dbquery.py: Query Nextcloud MariaDB with vertical/JSON output
- sqlitequery.py: Query MCP service SQLite DBs with service aliases
  (mcp, oauth, keycloak, basic) and column/JSON output modes
- Document both scripts in CLAUDE.md Database Inspection section

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

CLAUDE.md

@@ -239,6 +239,25 @@ uv run python -m tests.load.benchmark --output results.json --verbose
 
 **Credentials**: root/password, nextcloud/password, database: `nextcloud`
 
+### Quick Query Script (Recommended for Agents)
+
+Use `scripts/dbquery.py` for single SQL statements without requiring approval for each `docker compose exec`:
+
+```bash
+# Basic query
+./scripts/dbquery.py "SELECT COUNT(*) FROM oc_users"
+
+# Vertical output (one column per line) - useful for wide tables
+./scripts/dbquery.py -E "SELECT * FROM oc_oidc_clients LIMIT 1"
+
+# With different credentials
+./scripts/dbquery.py -u nextcloud -p nextcloud "SHOW TABLES"
+```
+
+### Direct Docker Access
+
+For interactive sessions or complex operations:
+
 ```bash
 # Connect to database
 docker compose exec db mariadb -u root -ppassword nextcloud
@@ -264,6 +283,40 @@ docker compose exec db mariadb -u root -ppassword nextcloud -e \
 - `oc_oidc_registration_tokens` - RFC 7592 registration tokens
 - `oc_oidc_redirect_uris` - Redirect URIs
 
+### SQLite Databases (MCP Services)
+
+Use `scripts/sqlitequery.py` to query SQLite databases in MCP service containers:
+
+```bash
+# List tables
+./scripts/sqlitequery.py ".tables"
+
+# Query specific service
+./scripts/sqlitequery.py -s oauth "SELECT * FROM refresh_tokens"
+./scripts/sqlitequery.py -s keycloak "SELECT * FROM oauth_clients"
+./scripts/sqlitequery.py -s basic "SELECT * FROM app_passwords"
+
+# With column headers
+./scripts/sqlitequery.py --column "SELECT * FROM audit_logs LIMIT 5"
+
+# JSON output
+./scripts/sqlitequery.py --json "SELECT * FROM oauth_sessions"
+
+# View schema
+./scripts/sqlitequery.py -s oauth ".schema refresh_tokens"
+```
+
+**Services**: `mcp` (default), `oauth`, `keycloak`, `basic`
+
+**SQLite Tables**:
+- `refresh_tokens` - OAuth refresh tokens with user profiles
+- `audit_logs` - Security audit trail
+- `oauth_clients` - DCR OAuth client credentials
+- `oauth_sessions` - OAuth flow session state
+- `registered_webhooks` - Webhook registrations
+- `app_passwords` - Multi-user BasicAuth passwords
+- `alembic_version` - Migration tracking
+
 ## Architecture Quick Reference
 
 **For detailed architecture, see:**