feat: basic POS & invoicing (closes groombook/groombook#5)

- Add invoice_status and payment_method enums to schema
- Add invoices table: appointmentId, clientId, subtotal/tax/tip/total cents,
  status (draft/pending/paid/void), paymentMethod, paidAt, notes
- Add invoice_line_items table: invoiceId, description, qty, unitPrice, total
- Migration 0002_invoices.sql with FK constraints and journal entry
- POST /api/invoices — create invoice with line items
- POST /api/invoices/from-appointment/:id — one-click invoice from appointment,
  pre-populated with service name and price; returns 409 if already invoiced
- GET /api/invoices — list with optional ?status/clientId/appointmentId filters
- GET /api/invoices/:id — invoice with line items
- PATCH /api/invoices/:id — update status, payment method, tip, notes; auto-sets
  paidAt when marking paid; blocks edits on voided invoices
- Add Invoice/InvoiceLineItem types to @groombook/types
- InvoicesPage: list view with status filter, create from appointment modal,
  detail modal with tip input, payment method selector, Mark as Paid/Void actions
- Add Invoices nav link in App.tsx

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

packages/db/migrations/0002_invoices.sql

@@ -0,0 +1,31 @@
+CREATE TYPE "public"."invoice_status" AS ENUM('draft', 'pending', 'paid', 'void');--> statement-breakpoint
+CREATE TYPE "public"."payment_method" AS ENUM('cash', 'card', 'check', 'other');--> statement-breakpoint
+CREATE TABLE "invoices" (
+	"id" uuid PRIMARY KEY DEFAULT gen_random_uuid() NOT NULL,
+	"appointment_id" uuid,
+	"client_id" uuid NOT NULL,
+	"subtotal_cents" integer NOT NULL,
+	"tax_cents" integer DEFAULT 0 NOT NULL,
+	"tip_cents" integer DEFAULT 0 NOT NULL,
+	"total_cents" integer NOT NULL,
+	"status" "invoice_status" DEFAULT 'draft' NOT NULL,
+	"payment_method" "payment_method",
+	"paid_at" timestamp,
+	"notes" text,
+	"created_at" timestamp DEFAULT now() NOT NULL,
+	"updated_at" timestamp DEFAULT now() NOT NULL
+);
+--> statement-breakpoint
+CREATE TABLE "invoice_line_items" (
+	"id" uuid PRIMARY KEY DEFAULT gen_random_uuid() NOT NULL,
+	"invoice_id" uuid NOT NULL,
+	"description" text NOT NULL,
+	"quantity" integer DEFAULT 1 NOT NULL,
+	"unit_price_cents" integer NOT NULL,
+	"total_cents" integer NOT NULL,
+	"created_at" timestamp DEFAULT now() NOT NULL
+);
+--> statement-breakpoint
+ALTER TABLE "invoices" ADD CONSTRAINT "invoices_appointment_id_appointments_id_fk" FOREIGN KEY ("appointment_id") REFERENCES "public"."appointments"("id") ON DELETE restrict ON UPDATE no action;--> statement-breakpoint
+ALTER TABLE "invoices" ADD CONSTRAINT "invoices_client_id_clients_id_fk" FOREIGN KEY ("client_id") REFERENCES "public"."clients"("id") ON DELETE restrict ON UPDATE no action;--> statement-breakpoint
+ALTER TABLE "invoice_line_items" ADD CONSTRAINT "invoice_line_items_invoice_id_invoices_id_fk" FOREIGN KEY ("invoice_id") REFERENCES "public"."invoices"("id") ON DELETE cascade ON UPDATE no action;

packages/db/migrations/meta/_journal.json

@@ -15,6 +15,13 @@
       "when": 1742241600000,
       "tag": "0001_pet_health_alerts",
       "breakpoints": true
+    },
+    {
+      "idx": 2,
+      "version": "7",
+      "when": 1773777600000,
+      "tag": "0002_invoices",
+      "breakpoints": true
     }
   ]
 }