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

.env.example

@@ -50,10 +50,27 @@ AI_PROVIDER=replicate
 REPLICATE_API_KEY=r8_PASTE_YOUR_KEY_HERE
 
 # ───────────────────────────────────────────────────────────────────────────
-# OPENAI (Alternative - not recommended, lower quality)
+# OPENAI (cloud, dall-e-3 / gpt-image-1)
 # Get key at: https://platform.openai.com/api-keys
+# AI_PROVIDER=openai
 # ───────────────────────────────────────────────────────────────────────────
 #OPENAI_API_KEY=sk-xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+#OPENAI_MODEL=dall-e-3
+
+# ───────────────────────────────────────────────────────────────────────────
+# INVOKEAI (self-hosted, best for Flux/SDXL)
+# Run InvokeAI on your local machine or NAS, point URL here.
+# AI_PROVIDER=invokeai
+# ───────────────────────────────────────────────────────────────────────────
+#INVOKEAI_URL=http://192.168.1.x:9090
+#INVOKEAI_DEFAULT_MODEL=flux-dev
+
+# ───────────────────────────────────────────────────────────────────────────
+# COMFYUI (self-hosted, workflow JSON API)
+# AI_PROVIDER=comfyui
+# ───────────────────────────────────────────────────────────────────────────
+#COMFYUI_URL=http://192.168.1.x:8188
+#COMFYUI_DEFAULT_MODEL=v1-5-pruned-emaonly.ckpt
 
 # ───────────────────────────────────────────────────────────────────────────
 # STABILITY AI (Alternative)