fix: resolve pre-existing test failures for content-aware-crop removal and watermark validation

- Replace content-aware-crop with ai-canvas-expand in TOOLS[], AI_TOOL_IDS,
  and FEATURE_BUNDLES (matching the already-updated tool-registry.tsx and
  feature-manifest.json from commit c6a5d3f)
- Fix trailing syntax error in features.ts (extra closing brace)
- Add ai-canvas-expand-settings mock to tool-registry test files
- Update watermark-image tests to expect 400 (validation rejection) instead
  of 422 (processing failure) for corrupted image buffers, matching the
  actual route behavior where validateImageBuffer catches them first

tests/unit/web/tool-registry.test.ts

@@ -181,6 +181,9 @@ vi.mock("@/components/tools/meme-generator-preview", () => ({
 vi.mock("@/components/tools/color-blindness-settings", () => ({
   ColorBlindnessSettings: () => null,
 }));
+vi.mock("@/components/tools/ai-canvas-expand-settings", () => ({
+  AiCanvasExpandSettings: () => null,
+}));
 
 // ---------------------------------------------------------------------------
 // Import after mocks