feat: add comprehensive test suite and CI pipeline

- Add 402 unit tests with 61.7% code coverage
- Add Vitest configuration with coverage reporting
- Extract testable utility functions from services
- Create test.yml workflow (runs on PR and push to main)
- Update docker-build.yml to require tests before building
- Add scheduler-utils.ts and server-config.ts for testable code

Test files added:
- auth.test.ts, medications.test.ts, planner.test.ts
- settings.test.ts, doses.test.ts, share.test.ts
- database.test.ts, server.test.ts, services.test.ts
- env.test.ts, translations.test.ts, integration.test.ts
- e2e-routes.test.ts, stock-calculation.test.ts

.github/workflows/test.yml

@@ -0,0 +1,75 @@
+name: Test
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+  # Allow this workflow to be called by other workflows
+  workflow_call:
+
+jobs:
+  # =============================================================================
+  # Backend Tests
+  # =============================================================================
+  backend-test:
+    name: Backend Tests
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: backend
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '22'
+          cache: 'npm'
+          cache-dependency-path: backend/package-lock.json
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: TypeScript type check
+        run: npx tsc --noEmit
+
+      - name: Run tests with coverage
+        run: npm run test:coverage
+
+      - name: Upload coverage report
+        uses: actions/upload-artifact@v4
+        if: always()
+        with:
+          name: backend-coverage
+          path: backend/coverage/
+          retention-days: 7
+
+  # =============================================================================
+  # Frontend Build Validation
+  # =============================================================================
+  frontend-build:
+    name: Frontend Build
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: frontend
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '22'
+          cache: 'npm'
+          cache-dependency-path: frontend/package-lock.json
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: TypeScript type check & build
+        run: npm run build