Add eslint flat-config for client and server and gate typecheck, lint and pages in CI

client and server had lint scripts but no eslint config (only shared was linted in CI). Add flat configs mirroring shared's stack (js + typescript-eslint recommended + eslint-config-prettier) plus the client's react-hooks/react-refresh plugins. Pre-existing patterns in this never-linted code (explicit any, require() in the CommonJS server, empty catches, exhaustive-deps) are set to 'warn' rather than 'error' so the gate passes at 0 errors without a repo-wide reformat — these can be ratcheted to errors over time. Wire blocking typecheck + lint + lint:pages steps into the client and server CI jobs (now that both typechecks are clean) and promote the server typecheck from informational to blocking.

.github/workflows/test.yml

@@ -57,12 +57,12 @@ jobs:
       - name: Build server (tsc -> dist)
         run: cd server && npm run build
 
-      - name: Typecheck (informational)
-        # Pre-existing type errors in the NestJS rewrite; surfaces them without
-        # blocking CI. Ratchet to blocking once the legacy code is cleaned up.
-        continue-on-error: true
+      - name: Typecheck
         run: cd server && npm run typecheck
 
+      - name: Lint
+        run: cd server && npm run lint:check
+
       - name: Run tests
         run: cd server && npm run test:coverage
 
@@ -93,6 +93,15 @@ jobs:
       - name: Build shared
         run: npm run build --workspace=shared
 
+      - name: Typecheck
+        run: cd client && npm run typecheck
+
+      - name: Lint
+        run: cd client && npm run lint:check
+
+      - name: Page pattern check
+        run: cd client && npm run lint:pages
+
       - name: Run tests
         run: cd client && npm run test:coverage