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- Remove reactflow dep (superseded by @xyflow/react), test harness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]>

app/backend/README_BACKEND.md

@@ -170,8 +170,7 @@ internal/
 ├── config/          - Configuration management
 ├── database/        - Database connections and migrations
 └── middleware/      - HTTP middleware
-migrations/          - SQL migration files
-migrations_goose/    - Goose-managed migrations for new schema changes
+migrations_goose/    - Goose-managed migrations (single migration path)
 ```
 
 ### Adding New Endpoints
@@ -179,9 +178,9 @@ migrations_goose/    - Goose-managed migrations for new schema changes
 1. Create handler functions in `internal/api/`
 2. Add routes in `internal/api/routes.go`
 3. Update database schema:
-   - Legacy chain lives in `migrations/` and is executed first.
-   - New migrations must be added to `migrations_goose/` using goose format (`-- +goose Up/Down`).
-   - Keep legacy files immutable after they are shipped.
+   - All migrations live in `migrations_goose/` using goose format (`-- +goose Up/Down`).
+   - `20260401163000_baseline.sql` carries the consolidated schema; append new files after it.
+   - Never edit the baseline in place; always add a new migration file.
 
 ### SQLC (Type-Safe Queries)