feat: add Phase 4 AI tools with Python bridge and 6 new tools

Add Python bridge (packages/ai/src/bridge.ts) that calls Python scripts
via child_process with venv-first fallback to system python3. Implements
6 AI-powered tools:

- Remove Background: rembg-based with U2-Net/IS-Net models
- Image Upscaling: Real-ESRGAN with Lanczos fallback
- OCR/Text Extraction: Tesseract + PaddleOCR engines
- Face/PII Blur: MediaPipe face detection with configurable blur
- Object Eraser: LaMa inpainting with mask-based input
- Smart Crop: Sharp attention-based entropy cropping (no Python needed)

Each tool includes: Python script, TypeScript wrapper, API route,
and React settings component. All Python scripts handle ImportError
gracefully with clear installation messages.

apps/api/src/routes/tools/index.ts

@@ -32,6 +32,13 @@ import { registerFavicon } from "./favicon.js";
 import { registerImageToPdf } from "./image-to-pdf.js";
 // Phase 3: Adjustments extra
 import { registerReplaceColor } from "./replace-color.js";
+// Phase 4: AI Tools
+import { registerRemoveBackground } from "./remove-background.js";
+import { registerUpscale } from "./upscale.js";
+import { registerOcr } from "./ocr.js";
+import { registerBlurFaces } from "./blur-faces.js";
+import { registerEraseObject } from "./erase-object.js";
+import { registerSmartCrop } from "./smart-crop.js";
 
 /**
  * Registry that imports and registers all tool routes.
@@ -79,5 +86,13 @@ export async function registerToolRoutes(app: FastifyInstance): Promise<void> {
   // Phase 3: Adjustments extra
   registerReplaceColor(app);
 
-  app.log.info("Tool routes registered (26 tools, 29 endpoints)");
+  // Phase 4: AI Tools
+  registerRemoveBackground(app);
+  registerUpscale(app);
+  registerOcr(app);
+  registerBlurFaces(app);
+  registerEraseObject(app);
+  registerSmartCrop(app);
+
+  app.log.info("Tool routes registered (32 tools, 35 endpoints)");
 }