feat: PWA Phase 2 — push notifications

Add web push notification support: push_subscriptions table (migration
0007), VAPID-based push service, subscribe/unsubscribe API routes, SW
push+notificationclick handlers, and subscribe UI on account page.
Triggers: new version uploaded (all project members) and version
approved/rejected (uploader).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/db/src/migrations/0007_push_subscriptions.sql

@@ -0,0 +1,12 @@
+CREATE TABLE "push_subscriptions" (
+	"id" uuid PRIMARY KEY DEFAULT gen_random_uuid() NOT NULL,
+	"user_id" uuid NOT NULL,
+	"endpoint" text NOT NULL,
+	"p256dh" text NOT NULL,
+	"auth" text NOT NULL,
+	"user_agent" text,
+	"created_at" timestamp DEFAULT now() NOT NULL,
+	CONSTRAINT "push_subscriptions_endpoint_unique" UNIQUE("endpoint")
+);
+--> statement-breakpoint
+ALTER TABLE "push_subscriptions" ADD CONSTRAINT "push_subscriptions_user_id_users_id_fk" FOREIGN KEY ("user_id") REFERENCES "public"."users"("id") ON DELETE cascade ON UPDATE no action;