fix: Replace npm ci with npm install in CI pipeline

Changed all npm ci commands to npm install because package-lock.json
is not present in the repository.

Changes:
- Replaced all `npm ci --legacy-peer-deps` with `npm install --legacy-peer-deps`
- Removed `cache: 'npm'` from all setup-node steps (requires package-lock.json)
- Applies to all CI jobs: lint, test, build, code-quality, integration-test, performance-test

This resolves the CI error:
"The npm ci command can only install with an existing package-lock.json"

The workflow will now successfully install dependencies and run all checks.

Author: claude

.github/workflows/ci.yml

@@ -19,10 +19,9 @@ jobs:
         uses: actions/setup-node@v4
         with:
           node-version: '18'
-          cache: 'npm'
 
       - name: Install dependencies
-        run: npm ci --legacy-peer-deps
+        run: npm install --legacy-peer-deps
 
       - name: Run ESLint
         run: npm run lint
@@ -45,10 +44,9 @@ jobs:
         uses: actions/setup-node@v4
         with:
           node-version: ${{ matrix.node-version }}
-          cache: 'npm'
 
       - name: Install dependencies
-        run: npm ci --legacy-peer-deps
+        run: npm install --legacy-peer-deps
 
       - name: Run tests
         run: npm test
@@ -77,10 +75,9 @@ jobs:
         uses: actions/setup-node@v4
         with:
           node-version: '20'
-          cache: 'npm'
 
       - name: Install dependencies
-        run: npm ci --legacy-peer-deps
+        run: npm install --legacy-peer-deps
 
       - name: Build project
         run: npm run build
@@ -114,10 +111,9 @@ jobs:
         uses: actions/setup-node@v4
         with:
           node-version: '20'
-          cache: 'npm'
 
       - name: Install dependencies
-        run: npm ci --legacy-peer-deps
+        run: npm install --legacy-peer-deps
 
       - name: Run tests with coverage
         run: npm test -- --coverage
@@ -233,10 +229,9 @@ jobs:
         uses: actions/setup-node@v4
         with:
           node-version: '20'
-          cache: 'npm'
 
       - name: Install dependencies
-        run: npm ci --legacy-peer-deps
+        run: npm install --legacy-peer-deps
 
       - name: Run integration tests
         run: npm test -- --testPathPattern=integration
@@ -264,10 +259,9 @@ jobs:
         uses: actions/setup-node@v4
         with:
           node-version: '20'
-          cache: 'npm'
 
       - name: Install dependencies
-        run: npm ci --legacy-peer-deps
+        run: npm install --legacy-peer-deps
 
       - name: Run performance benchmarks
         run: |