chore: restore production build cache with stable key using actions/cache (#26276)

* fix: align env vars between Production Builds and E2E workflows for turbo cache sharing

Co-Authored-By: keith@cal.com <keithwillcode@gmail.com>

* fix: move E2E-specific env vars to step-level for turbo cache alignment

Instead of adding env vars to production-build-without-database.yml (which
caused DB calls during build), move the E2E-specific env vars from workflow-level
to step-level in e2e.yml. This ensures the cache-build step has the same env
context in both workflows, enabling turbo remote cache sharing.

Env vars moved to step-level:
- DATABASE_DIRECT_URL (to cache-db and Run Tests steps)
- E2E_TEST_MAILHOG_ENABLED (to Run Tests step)
- EMAIL_SERVER_* (to Run Tests step)

Co-Authored-By: keith@cal.com <keithwillcode@gmail.com>

* fix: restore production build cache with stable key using actions/cache

- Restore artifact caching for .next, dist, and .turbo directories
- Use actions/cache@v4 (accelerated by Blacksmith on their runners)
- Design stable cache key scoped to branch:
  - Includes branch name (head_ref for PRs, ref_name for pushes)
  - Hashes yarn.lock for dependency changes
  - Hashes source files in apps/web and packages/*/src
  - Excludes generated directories (prisma/zod, kysely) that caused instability
- Add restore-keys for partial cache hits
- Only run yarn build on cache miss
- Revert e2e.yml env var changes (no longer needed with artifact caching)

Co-Authored-By: keith@cal.com <keithwillcode@gmail.com>

* fix: simplify restore-keys to single fallback

Co-Authored-By: keith@cal.com <keithwillcode@gmail.com>

* fix: remove restore-keys entirely for exact cache matching only

Co-Authored-By: keith@cal.com <keithwillcode@gmail.com>

* fix: use broader package pattern with exclusions for generated prisma files

Co-Authored-By: keith@cal.com <keithwillcode@gmail.com>

* fix: add exclusions for prisma/generated and prisma/client directories

Co-Authored-By: keith@cal.com <keithwillcode@gmail.com>

* Apply suggestion from @cubic-dev-ai[bot]

Co-authored-by: cubic-dev-ai[bot] <191113872+cubic-dev-ai[bot]@users.noreply.github.com>

* fix: add .json and .css patterns to cache hash for config and style changes

Co-Authored-By: keith@cal.com <keithwillcode@gmail.com>

---------

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Co-authored-by: cubic-dev-ai[bot] <191113872+cubic-dev-ai[bot]@users.noreply.github.com>

.github/actions/cache-build/action.yml

@@ -7,7 +7,27 @@ inputs:
 runs:
   using: "composite"
   steps:
+    - name: Cache production build
+      uses: actions/cache@v4
+      id: cache-build
+      env:
+        cache-name: prod-build
+        # Use branch name for cache scoping (head_ref for PRs, ref_name for pushes)
+        branch-key: ${{ github.head_ref || github.ref_name }}
+        # Hash yarn.lock for dependency changes
+        lockfile-hash: ${{ hashFiles('yarn.lock') }}
+        # Hash source files that affect the web build, excluding generated directories
+        # Excludes packages/prisma/{generated,client,zod}/* and packages/kysely/* which are generated by prisma generate
+        source-hash: ${{ hashFiles('apps/**/**.[jt]s', 'apps/**/**.[jt]sx', 'apps/**/*.json', 'apps/**/*.css', 'packages/**/**.[jt]s', 'packages/**/**.[jt]sx', 'packages/prisma/schema.prisma', 'packages/prisma/migrations/**/*.sql', '!**/node_modules/**', '!packages/prisma/generated/**', '!packages/prisma/client/**', '!packages/prisma/zod/**', '!packages/kysely/**') }}
+      with:
+        path: |
+          ${{ github.workspace }}/apps/web/.next
+          ${{ github.workspace }}/apps/web/public/embed
+          **/.turbo/**
+          **/dist/**
+        key: ${{ runner.os }}-${{ env.cache-name }}-${{ inputs.node_version }}-${{ env.branch-key }}-${{ env.lockfile-hash }}-${{ env.source-hash }}
     - run: |
         export NODE_OPTIONS="--max_old_space_size=8192"
         yarn build
+      if: steps.cache-build.outputs.cache-hit != 'true'
       shell: bash