fix(ci): simplify workflow to avoid external GitHub actions

The previous workflow was getting stuck because it was trying to pull
actions from GitHub (https://github.com/actions/cache@v3) which can
cause connectivity and compatibility issues in Forgejo.

Changes:
- Remove all external GitHub action dependencies except checkout
- Use Forgejo's built-in checkout@v4 action
- Remove caching steps (can be added later with Forgejo-native actions)
- Add explicit dependency installation step
- Use 'cargo build --release' for better optimization

This should make the CI more reliable and faster to start.

.forgejo/workflows/lint-and-build.yml

@@ -22,25 +22,11 @@ jobs:
       image: rust:latest
     steps:
       - name: Checkout code
-        uses: https://github.com/actions/checkout@v4
+        uses: actions/checkout@v4
 
-      - name: Cache cargo registry
+      - name: Install dependencies
-        uses: https://github.com/actions/cache@v3
+        run: |
-        with:
+          apt-get update && apt-get install -y pkg-config libssl-dev
-          path: ~/.cargo/registry
-          key: ${{ runner.os }}-cargo-registry-${{ hashFiles('**/Cargo.lock') }}
-
-      - name: Cache cargo index
-        uses: https://github.com/actions/cache@v3
-        with:
-          path: ~/.cargo/git
-          key: ${{ runner.os }}-cargo-index-${{ hashFiles('**/Cargo.lock') }}
-
-      - name: Cache cargo build
-        uses: https://github.com/actions/cache@v3
-        with:
-          path: backend/target
-          key: ${{ runner.os }}-cargo-build-target-${{ hashFiles('**/Cargo.lock') }}
 
       - name: Run rustfmt
         working-directory: ./backend
@@ -60,30 +46,16 @@ jobs:
     needs: lint
     steps:
       - name: Checkout code
-        uses: https://github.com/actions/checkout@v4
+        uses: actions/checkout@v4
 
-      - name: Cache cargo registry
+      - name: Install dependencies
-        uses: https://github.com/actions/cache@v3
+        run: |
-        with:
+          apt-get update && apt-get install -y pkg-config libssl-dev
-          path: ~/.cargo/registry
-          key: ${{ runner.os }}-cargo-registry-${{ hashFiles('**/Cargo.lock') }}
-
-      - name: Cache cargo index
-        uses: https://github.com/actions/cache@v3
-        with:
-          path: ~/.cargo/git
-          key: ${{ runner.os }}-cargo-index-${{ hashFiles('**/Cargo.lock') }}
-
-      - name: Cache cargo build
-        uses: https://github.com/actions/cache@v3
-        with:
-          path: backend/target
-          key: ${{ runner.os }}-cargo-build-target-${{ hashFiles('**/Cargo.lock') }}
 
       - name: Build project
         working-directory: ./backend
         run: |
-          cargo build --verbose
+          cargo build --release --verbose
 
       - name: Run tests
         working-directory: ./backend
@@ -101,7 +73,7 @@ jobs:
         image: docker:dind
     steps:
       - name: Checkout code
-        uses: https://github.com/actions/checkout@v4
+        uses: actions/checkout@v4
 
       - name: Build Docker image
         working-directory: ./backend