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/config.py

@@ -12,13 +12,24 @@ class Settings(BaseSettings):
     access_token_expire_minutes: int = 30
 
     # AI Provider
-    ai_provider: str = "mock"  # Options: openai, stability, replicate, mock
+    # Local: blank or "mock" — always available, no config needed
+    # Remote (set ONE): openai | invokeai | comfyui | replicate | stability
+    ai_provider: str = "mock"
 
     # Provider API Keys
     openai_api_key: str = ""
+    openai_model: str = "dall-e-3"
     stability_api_key: str = ""
     replicate_api_key: str = ""
 
+    # InvokeAI (self-hosted)
+    invokeai_url: str = ""
+    invokeai_default_model: str = "flux-dev"
+
+    # ComfyUI (self-hosted)
+    comfyui_url: str = ""
+    comfyui_default_model: str = "v1-5-pruned-emaonly.ckpt"
+
     # Model Selection (optional, provider-specific)
     stability_model: str = "sdxl"  # Options: sdxl, sd15, sd21
     replicate_model: str = "sdxl-inpaint"  # Options: sdxl-inpaint, lama, realistic-vision