feat: add missing features from main merge

1. Built-in tool type seeding (apps/api/src/seeds/builtin_tool_types.py):
   - Seeds code-server, jupyter-notebook, and opencode on startup.
   - Adapts to current dev model: uses interface_type (single string)
     instead of interfaces array, and created_by_id=None instead of
     is_builtin flag.
   - Called from main.py startup event.

2. Config profile default management:
   - Adds default_profile_id and default_profiles properties to
     UserConfig model for JSON-backed per-tool-type defaults.
   - Adds GET /config-profiles/defaults, PUT /config-profiles/defaults,
     and GET /config-profiles/defaults/{tool_type_id} endpoints.
   - Validates that all profile IDs in default mappings belong to the
     authenticated user before persisting.

3. Config profile unique constraint:
   - Adds __table_args__ with UniqueConstraint(user_id, name) to
     ConfigProfile model. The constraint already exists in the DB
     from migration 2026_05_24_add_config_profiles.py; this just
     aligns the SQLAlchemy model with the schema.

Quality gates: py_compile passed, ruff passed on all modified files.

apps/api/src/main.py

@@ -37,6 +37,7 @@ from src.logging_config import (
     RequestLoggingMiddleware,
     configure_logging,
 )
+from src.seeds.builtin_tool_types import seed_builtin_tool_types
 from src.services.correlation import CorrelationIdMiddleware
 from src.services.event_bus import InstanceEventBus
 from src.services.health_monitor import HealthMonitor
@@ -135,6 +136,10 @@ async def on_startup():
     _health_monitor.start()
     logger.info("Health monitor started")
 
+    # Seed built-in tool types
+    await seed_builtin_tool_types()
+    logger.info("Built-in tool types seeded")
+
     logger.info("Startup complete.")