feat(db): Postgres schema, migrations and defects repository (T3)

Drizzle schema for projects, defects, push_subscriptions (C8); generated
migration; a defects repository (createDefect / listRecentDefects); a
programmatic migrator; and a db:verify script. section_id is a plain string
referencing in-code board ids, no FK (ADR 0001). Verified against real
Postgres: migration applies, a defect round-trips, /api/health reports db up.

server/db/migrations/0000_loving_black_bird.sql

@@ -0,0 +1,27 @@
+CREATE TABLE "defects" (
+	"id" uuid PRIMARY KEY NOT NULL,
+	"section_id" text NOT NULL,
+	"project_id" uuid NOT NULL,
+	"verbatim" text NOT NULL,
+	"reporter_email" text NOT NULL,
+	"created_at" timestamp with time zone DEFAULT now() NOT NULL
+);
+--> statement-breakpoint
+CREATE TABLE "projects" (
+	"id" uuid PRIMARY KEY NOT NULL,
+	"name" text NOT NULL,
+	"created_at" timestamp with time zone DEFAULT now() NOT NULL,
+	CONSTRAINT "projects_name_unique" UNIQUE("name")
+);
+--> statement-breakpoint
+CREATE TABLE "push_subscriptions" (
+	"id" uuid PRIMARY KEY NOT NULL,
+	"endpoint" text NOT NULL,
+	"p256dh" text NOT NULL,
+	"auth" text NOT NULL,
+	"reporter_email" text,
+	"created_at" timestamp with time zone DEFAULT now() NOT NULL,
+	CONSTRAINT "push_subscriptions_endpoint_unique" UNIQUE("endpoint")
+);
+--> statement-breakpoint
+ALTER TABLE "defects" ADD CONSTRAINT "defects_project_id_projects_id_fk" FOREIGN KEY ("project_id") REFERENCES "public"."projects"("id") ON DELETE no action ON UPDATE no action;