feat: deterministic seed, impersonation migration, test factories (GRO-110)

Phase 1 — Seed Hardening:
- Replace all Math.random() calls in seed.ts with a Mulberry32 seeded PRNG
  (seed 42) so the same data set is reproduced on every run
- Replace crypto.randomUUID() with a PRNG-based UUID v4 generator
- Add manager (Jordan Lee) and receptionist (Sam Rivera) staff members
  to seed — previously all staff were groomers
- New packages/db/src/reset.ts drops all tables/enums and re-runs
  migrate + seed; exposed as `pnpm db:reset` at root
- Generate migration 0010_impersonation_sessions.sql for the
  impersonation_sessions and impersonation_audit_logs tables that were
  already in schema.ts but had no corresponding migration

Phase 2 — Test Factories:
- New packages/db/src/factories.ts with buildStaff, buildClient, buildPet,
  buildService, buildAppointment and resetFactoryCounters helpers
- Exported via @groombook/db/factories subpath (package.json + vitest alias)
- impersonation.test.ts updated to use buildStaff instead of hand-rolled
  fixture objects

Closes #90 (Phases 1 + 2)

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

packages/db/migrations/0010_impersonation_sessions.sql

@@ -0,0 +1,26 @@
+-- Create impersonation_session_status enum and tables
+CREATE TYPE "impersonation_session_status" AS ENUM ('active', 'ended', 'expired');
+
+CREATE TABLE "impersonation_sessions" (
+	"id" uuid PRIMARY KEY DEFAULT gen_random_uuid() NOT NULL,
+	"staff_id" uuid NOT NULL,
+	"client_id" uuid NOT NULL,
+	"reason" text,
+	"status" "impersonation_session_status" DEFAULT 'active' NOT NULL,
+	"started_at" timestamp DEFAULT now() NOT NULL,
+	"ended_at" timestamp,
+	"expires_at" timestamp NOT NULL,
+	"created_at" timestamp DEFAULT now() NOT NULL,
+	CONSTRAINT "impersonation_sessions_staff_id_staff_id_fk" FOREIGN KEY ("staff_id") REFERENCES "staff"("id") ON DELETE restrict,
+	CONSTRAINT "impersonation_sessions_client_id_clients_id_fk" FOREIGN KEY ("client_id") REFERENCES "clients"("id") ON DELETE restrict
+);
+
+CREATE TABLE "impersonation_audit_logs" (
+	"id" uuid PRIMARY KEY DEFAULT gen_random_uuid() NOT NULL,
+	"session_id" uuid NOT NULL,
+	"action" text NOT NULL,
+	"page_visited" text,
+	"metadata" jsonb,
+	"created_at" timestamp DEFAULT now() NOT NULL,
+	CONSTRAINT "impersonation_audit_logs_session_id_impersonation_sessions_id_fk" FOREIGN KEY ("session_id") REFERENCES "impersonation_sessions"("id") ON DELETE cascade
+);

packages/db/migrations/meta/_journal.json

@@ -71,6 +71,13 @@
       "when": 1773993600000,
       "tag": "0009_client_soft_delete",
       "breakpoints": true
+    },
+    {
+      "idx": 10,
+      "version": "7",
+      "when": 1742500800000,
+      "tag": "0010_impersonation_sessions",
+      "breakpoints": true
     }
   ]
 }