fix(app): teach the bundler the repo's .js -> .ts import convention

The control-plane app follows the repo-wide ESM convention - a './x.js'
specifier for a './x.ts' source - in all 79 of its relative imports.
TypeScript resolves that (moduleResolution: bundler), webpack does not, so
the new `next build` gate step failed with "Module not found: Can't resolve
'../../../../lib/db.js'" on the first app build this repo ever ran.

resolve.extensionAlias maps a '.js' request to the '.ts'/'.tsx' source
behind it, so the bundler honours the same convention the type-checker and
the packages already do. One resolver-level change, no import churn.

Evidence: run 69747, job 72065 - the app-build step fails to compile with
5 module-not-found errors across 4 route files.

apps/control-plane/next.config.mjs

@@ -1,5 +1,22 @@
 /** @type {import('next').NextConfig} */
 const nextConfig = {
   transpilePackages: ["@coreci/db", "@coreci/auth", "@coreci/secrets", "@coreci/config", "@coreci/runtime", "@coreci/byom"],
+  // The app follows the repo-wide ESM import convention - a "./x.js" specifier
+  // for a "./x.ts" source - like every package in this repo. TypeScript
+  // resolves that convention (moduleResolution: bundler); the bundler does
+  // not, so `next build` failed with "Module not found: Can't resolve
+  // '../../../../lib/db.js'". resolve.extensionAlias maps a ".js" request to
+  // the ".ts"/".tsx" source behind it, so the bundler honours the same
+  // convention the type-checker and the packages already do - one
+  // resolver-level change, no import churn.
+  webpack: (config) => {
+    config.resolve.extensionAlias = {
+      ...config.resolve.extensionAlias,
+      ".js": [".ts", ".tsx", ".js"],
+      ".mjs": [".mts", ".mjs"],
+      ".cjs": [".cts", ".cjs"],
+    };
+    return config;
+  },
 };
-export default nextConfig;
+export default nextConfig;