docs/ci: note unit tests in README, gate release build to master

.github/workflows/ci.yml

@@ -11,7 +11,7 @@ env:
 
 jobs:
   ci:
-    name: Check / Test / Build
+    name: Check / Test
     runs-on: ubuntu-latest
 
     steps:
@@ -38,5 +38,27 @@ jobs:
       - name: test
         run: cargo test
 
+  release-build:
+    name: Release build
+    runs-on: ubuntu-latest
+    if: github.ref == 'refs/heads/master' && github.event_name == 'push'
+    needs: ci
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install Rust stable
+        uses: dtolnay/rust-toolchain@stable
+
+      - name: Cache cargo
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            target
+          key: ${{ runner.os }}-cargo-release-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: ${{ runner.os }}-cargo-release-
+
       - name: build (release)
         run: cargo build --release -p presentation -p worker

README.md

@@ -153,9 +153,12 @@ Supports review logging, bulk CSV import (column order matches the export format
 ## Test
 
 ```bash
-cargo test
+cargo test           # full workspace (requires DATABASE_URL for sqlx offline checks)
+cargo test -p application   # domain-level unit tests only — no database required
 ```
 
+The `application` crate has unit tests for core use cases (`log_review`, `register`, `login`, `add_to_watchlist`, `delete_review`) backed by in-memory fakes from `domain`'s `test-helpers` feature. These run without a database and are the fastest feedback loop for business logic changes.
+
 ## Docker
 
 The image contains both `presentation` (HTTP server) and `worker` (event processor). Run them as separate containers sharing the same data volume: