refactor: inline packages/db and packages/types into api package

Phase 2 extraction: groombook/api from groombook/app monorepo.

Changes:
- Move packages/db content to apps/api/src/db/
- Move packages/types content to apps/api/src/types/
- Inline database schema and migrations into api package
- Update Dockerfile to build single package
- Update CI workflow for single-package structure
- Fix vitest.config.ts aliases

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/api/migrations/0013_appointment_confirmation.sql

@@ -0,0 +1,7 @@
+ALTER TABLE appointments
+  ADD COLUMN confirmation_status TEXT NOT NULL DEFAULT 'pending',
+  ADD COLUMN confirmed_at TIMESTAMPTZ,
+  ADD COLUMN cancelled_at TIMESTAMPTZ,
+  ADD COLUMN confirmation_token TEXT UNIQUE;
+
+CREATE INDEX idx_appointments_confirmation_token ON appointments (confirmation_token) WHERE confirmation_token IS NOT NULL;