feat: configure eslint with unused import removal (#564)

* feat: configure eslint with unused import removal

Add ESLint v9 (flat config) for code quality:
- eslint-plugin-unused-imports for auto-removing dead imports
- @typescript-eslint for TypeScript-aware linting
- eslint-plugin-react-hooks for React hooks rules
- eslint-config-prettier to avoid formatting conflicts
- lint-staged runs eslint --fix before prettier on .ts/.tsx
- CI lint job added to ci-quality.yml

* refactor: remove unused imports via eslint --fix

Auto-fixed by eslint-plugin-unused-imports. No logic changes.

* chore: add eslint fix commit to .git-blame-ignore-revs

.github/workflows/ci-quality.yml

@@ -17,6 +17,19 @@ jobs:
       - run: npm ci
       - run: npx prettier --check .
 
+  lint:
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+      - uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4
+        with:
+          node-version: 20
+          cache: npm
+          cache-dependency-path: package-lock.json
+      - run: npm ci
+      - run: npx eslint .
+
   typecheck:
     runs-on: ubuntu-latest
     timeout-minutes: 10