Migrate harness from in-memory stores to CloudNativePG

Replace all in-memory Map-backed stores (credentials, models, agents,
tasks, iterations, usage) with Drizzle ORM queries against the
homelab-pg PostgreSQL cluster. All store functions are now async.

- Add 6 harness_* tables to @homelab/db schema
- Generate and apply initial Drizzle migration
- Add lazy DB connection proxy to avoid build-time errors
- Wire DATABASE_URL from sealed secret into harness deployment
- Update all API routes, orchestrator, executor, and boot to await
  async store operations

packages/db/drizzle/0000_sparkling_gressill.sql

@@ -0,0 +1,85 @@
+CREATE TABLE IF NOT EXISTS "harness_agent_configs" (
+	"id" text PRIMARY KEY NOT NULL,
+	"name" text NOT NULL,
+	"runtime" text NOT NULL,
+	"model_id" text NOT NULL,
+	"provider" text NOT NULL,
+	"max_tokens" integer,
+	"env" jsonb,
+	"created_at" timestamp DEFAULT now() NOT NULL,
+	"updated_at" timestamp DEFAULT now() NOT NULL
+);
+--> statement-breakpoint
+CREATE TABLE IF NOT EXISTS "harness_credentials" (
+	"id" text PRIMARY KEY NOT NULL,
+	"provider" text NOT NULL,
+	"label" text NOT NULL,
+	"token" text NOT NULL,
+	"base_url" text,
+	"created_at" timestamp DEFAULT now() NOT NULL,
+	"updated_at" timestamp DEFAULT now() NOT NULL
+);
+--> statement-breakpoint
+CREATE TABLE IF NOT EXISTS "harness_curated_models" (
+	"id" text PRIMARY KEY NOT NULL,
+	"name" text NOT NULL,
+	"provider" text NOT NULL,
+	"enabled" boolean DEFAULT true NOT NULL,
+	"context_window" integer,
+	"cost_per_1k_input" real,
+	"cost_per_1k_output" real,
+	"created_at" timestamp DEFAULT now() NOT NULL,
+	"updated_at" timestamp DEFAULT now() NOT NULL
+);
+--> statement-breakpoint
+CREATE TABLE IF NOT EXISTS "harness_iterations" (
+	"id" serial PRIMARY KEY NOT NULL,
+	"task_id" text NOT NULL,
+	"n" integer NOT NULL,
+	"status" text DEFAULT 'pending' NOT NULL,
+	"diagnosis" text,
+	"agent_output" text,
+	"evals" jsonb,
+	"diff_stats" text,
+	"started_at" bigint,
+	"completed_at" bigint
+);
+--> statement-breakpoint
+CREATE TABLE IF NOT EXISTS "harness_model_usage" (
+	"id" serial PRIMARY KEY NOT NULL,
+	"model_id" text NOT NULL,
+	"provider" text NOT NULL,
+	"task_id" text NOT NULL,
+	"task_slug" text NOT NULL,
+	"iteration" integer NOT NULL,
+	"input_tokens" integer NOT NULL,
+	"output_tokens" integer NOT NULL,
+	"duration_ms" integer NOT NULL,
+	"timestamp" bigint NOT NULL
+);
+--> statement-breakpoint
+CREATE TABLE IF NOT EXISTS "harness_tasks" (
+	"id" text PRIMARY KEY NOT NULL,
+	"slug" text NOT NULL,
+	"goal" text NOT NULL,
+	"status" text DEFAULT 'pending' NOT NULL,
+	"iteration" integer DEFAULT 0 NOT NULL,
+	"max_iterations" integer DEFAULT 6 NOT NULL,
+	"started_at" bigint,
+	"completed_at" bigint,
+	"project" text DEFAULT '—' NOT NULL,
+	"evals" jsonb DEFAULT '{}'::jsonb NOT NULL,
+	"pr" jsonb,
+	"spec" jsonb NOT NULL,
+	"created_at" timestamp DEFAULT now() NOT NULL,
+	"updated_at" timestamp DEFAULT now() NOT NULL
+);
+--> statement-breakpoint
+CREATE TABLE IF NOT EXISTS "users" (
+	"id" serial PRIMARY KEY NOT NULL,
+	"email" text NOT NULL,
+	"name" text,
+	"created_at" timestamp DEFAULT now() NOT NULL,
+	"updated_at" timestamp DEFAULT now() NOT NULL,
+	CONSTRAINT "users_email_unique" UNIQUE("email")
+);