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

apps/harness/src/lib/repo-search.ts

@@ -1,4 +1,4 @@
-import { getCredentialsByProvider } from "./credentials";
+import { getRawCredentialsByProvider } from "./credentials";
 
 export interface RepoResult {
   provider: "github" | "gitlab";
@@ -21,7 +21,7 @@ export async function searchRepos(query: string): Promise<RepoResult[]> {
 }
 
 async function searchGitHub(query: string): Promise<RepoResult[]> {
-  const creds = getCredentialsByProvider("github");
+  const creds = await getRawCredentialsByProvider("github");
   if (creds.length === 0) return [];
 
   const results: RepoResult[] = [];
@@ -61,7 +61,7 @@ async function searchGitHub(query: string): Promise<RepoResult[]> {
 }
 
 async function searchGitLab(query: string): Promise<RepoResult[]> {
-  const creds = getCredentialsByProvider("gitlab");
+  const creds = await getRawCredentialsByProvider("gitlab");
   if (creds.length === 0) return [];
 
   const results: RepoResult[] = [];