fix(ci): remove npm cache dependency on package-lock.json

Use npm install instead of npm ci since package-lock.json files
are not committed to the repository.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -20,13 +20,11 @@ jobs:
         uses: actions/setup-node@v4
         with:
           node-version: '20'
-          cache: 'npm'
-          cache-dependency-path: backend/package-lock.json
 
       - name: Install backend dependencies
         run: |
           cd backend
-          npm ci
+          npm install
 
       - name: Run ESLint (backend)
         run: |
@@ -48,13 +46,11 @@ jobs:
         uses: actions/setup-node@v4
         with:
           node-version: '20'
-          cache: 'npm'
-          cache-dependency-path: frontend/package-lock.json
 
       - name: Install frontend dependencies
         run: |
           cd frontend
-          npm ci
+          npm install
 
       - name: Run ESLint (frontend)
         run: |
@@ -72,13 +68,11 @@ jobs:
         uses: actions/setup-node@v4
         with:
           node-version: '20'
-          cache: 'npm'
-          cache-dependency-path: frontend/package-lock.json
 
       - name: Install frontend dependencies
         run: |
           cd frontend
-          npm ci
+          npm install
 
       - name: Build frontend
         run: |