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/0004_reminder_logs.sql

@@ -0,0 +1,11 @@
+-- Add email opt-out flag to clients
+ALTER TABLE "clients" ADD COLUMN "email_opt_out" boolean NOT NULL DEFAULT false;
+
+-- Track sent reminders to prevent duplicate sends
+CREATE TABLE "reminder_logs" (
+	"id" uuid PRIMARY KEY DEFAULT gen_random_uuid() NOT NULL,
+	"appointment_id" uuid NOT NULL REFERENCES "appointments"("id") ON DELETE CASCADE,
+	"reminder_type" text NOT NULL,
+	"sent_at" timestamp DEFAULT now() NOT NULL,
+	UNIQUE ("appointment_id", "reminder_type")
+);