ci: cache next.js build output and parallelize checks with build

.github/workflows/ci.yml

@@ -6,7 +6,7 @@ on:
   pull_request:
 
 jobs:
-  verify:
+  checks:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
@@ -28,10 +28,32 @@ jobs:
 
       - run: pnpm format:check
 
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: pnpm/action-setup@v4
+        with:
+          version: 10.33.3
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 22
+          cache: pnpm
+
+      - run: pnpm install --frozen-lockfile
+
+      - uses: actions/cache@v4
+        with:
+          path: .next/cache
+          key: ${{ runner.os }}-nextjs-${{ hashFiles('pnpm-lock.yaml') }}-${{ hashFiles('src/**/*.ts', 'src/**/*.tsx', 'src/**/*.css') }}
+          restore-keys: |
+            ${{ runner.os }}-nextjs-${{ hashFiles('pnpm-lock.yaml') }}-
+            ${{ runner.os }}-nextjs-
+
       - run: pnpm build
         env:
-          # Build only — no DB connection. Provide a placeholder so any
-          # module-level reads of DATABASE_URL don't crash the build.
           DATABASE_URL: postgres://placeholder:placeholder@localhost:5432/placeholder
           AUTH_SECRET: ci-placeholder-secret
           NEXT_PUBLIC_APP_URL: http://localhost:3000