Consolidate backend: drop vendored APwhy, converge on goose + sqlc

Phase 0 cleanup verified end-to-end:

- Delete vendored APwhy runtime (cmd/apwhy, internal/apwhy) and the
  unwired copy (internal/api/server.go + static bundle + cloned
  internal/{storage,analytics,auth,rbac}) — ~7.5k lines of dead code.
- Keep Containr's native internal/gateway; move APwhy management
  routes under /api/v1/gateway/* so they stop colliding with the
  native /services paths. Fix handlers against the real schema:
  UUID ids via RETURNING, integer enabled flags, plan validation,
  service validate endpoint, unique-violation mapping.
- Port agents.go off GORM onto sqlc (sqlc/queries/agents.sql);
  drop gorm dependencies; fix sqlc schema drift (services.environment_id).
- Replace the SELECT 1 goose baseline with the real consolidated
  schema (52 tables) minus APwhy's parallel auth/RBAC objects;
  idempotent via IF NOT EXISTS / OR REPLACE / guarded DO blocks so it
  replays cleanly over legacy installs. Add a drop migration for the
  dead objects and delete the legacy filename-tracked migrations/
  loader, directory, and Dockerfile copy. Verified via cmd/migrate:
  fresh install 53 tables, legacy upgrade clean to 20260917000000.
- Canvas: add invisible React Flow handles to ServiceNode so inferred
  auto-connections stop emitting warning #008.
- Remove reactflow dep (superseded by @xyflow/react), test harness
  cmds, and legacy 0001_init.sql backups.

Authored By: TDvorak <[email protected]>

docs/developers/onboarding.md

@@ -137,7 +137,7 @@ containr/
 │   ├── proxmox/         # Proxmox integration
 │   ├── scaling/          # Auto-scaling engine
 │   └── security/        # Security scanning
-├── migrations/           # Database migrations
+├── migrations_goose/     # Goose-managed database migrations
 ├── pkg/                 # Public library code
 ├── scripts/             # Build and utility scripts
 ├── src/                 # Frontend source code
@@ -162,7 +162,7 @@ git checkout -b feature/your-feature-name
 
 #### Backend Changes
 - Add new API endpoints in `internal/api/`
-- Update database schema in `migrations/`
+- Update database schema in `migrations_goose/` (goose format: `-- +goose Up/Down`)
 - Add tests in `tests/`
 - Update documentation