Add LaMa magic eraser, remote provider abstraction, and AI tool infrastructure

Backend:
- requirements.txt: add simple-lama-inpainting, rembg[gpu]; upgrade opencv to 4.10+
- app/config.py: add InvokeAI (url, model) and ComfyUI (url, model) settings; OPENAI_MODEL
- app/services/local_inpaint.py: LaMa, OpenCV, rembg wrappers (auto GPU/CPU)
- app/services/remote_provider.py: abstract RemoteAIProvider + OpenAI, InvokeAI, ComfyUI drivers
- app/routers/ai_tools.py: new /api/* endpoints — /erase, /inpaint/lama, /inpaint/fast,
  /background/remove, /inpaint/remote, /generate/txt2img, /generate/img2img,
  /generate/outpaint, GET /config (capability flags)
- app/main.py: register ai_tools router

Frontend:
- services/api.js: add erase(), textToImage(), imageToImage(), remoteInpaint(), getConfig()
- api/capabilities.js: lazy-fetch /api/config singleton; hasRemote() helper
- tools/ai_lama_erase.js: brush-paint mask → LaMa erase → apply to layer
- tools/ai_smart_inpaint.js: brush mask + dialog (Fast/Quality mode + prompt) → inpaint
- core/components/provider-badge.js: shows active provider + health in toolbar
- config.js: register ai_lama_erase and ai_smart_inpaint tools
- main.js: mount provider badge on load
- .env.example: document InvokeAI, ComfyUI, OpenAI provider settings

https://claude.ai/code/session_01B58MaJCU1R6KwBDJCp8AfN

backend/app/main.py

@@ -8,7 +8,7 @@ import os
 
 from app.config import settings
 from app.database import init_db
-from app.routers import projects, edits, images, patches, generate, tools
+from app.routers import projects, edits, images, patches, generate, tools, ai_tools
 
 
 @asynccontextmanager
@@ -41,6 +41,7 @@ app.include_router(images.router)
 app.include_router(patches.router)
 app.include_router(generate.router)
 app.include_router(tools.router)
+app.include_router(ai_tools.router)
 
 
 @app.get("/api")