Implement complete AI Photo Edit tool with mask-scoped regeneration

This commit implements a full-stack AI photo editing application that
allows users to regenerate only selected areas of images using AI.

Features implemented:
- Frontend (React + Fabric.js):
  * Interactive canvas with selection tools (rectangle, ellipse, lasso)
  * Real-time selection preview and editing
  * Mode toggle (A: patch only, B: patch + context)
  * Feather slider for edge blending (0-50px)
  * Prompt input for AI instructions
  * Edit history viewer with revert capability
  * Responsive UI with dark theme

- Backend (FastAPI):
  * RESTful API for projects and edits
  * SQLite database for metadata storage
  * Image processing pipeline with PIL/OpenCV
  * AI provider interface (pluggable)
  * Support for OpenAI, Stability AI, and mock providers
  * Feathered alpha blending for smooth compositing
  * Complete edit history tracking
  * File-based storage for images and edits

- Image Processing:
  * Patch extraction from bounding boxes
  * Mask generation for all selection types
  * Feathered edge blending
  * Patch compositing back to full image
  * No pixels modified outside selection
  * All edits reversible

- Infrastructure:
  * Docker Compose orchestration
  * Production and development configurations
  * Nginx reverse proxy for frontend
  * Hot-reload support for development
  * Volume persistence for data

Architecture follows specification exactly:
- Only selected regions are regenerated
- Full image pixels preserved outside mask
- Two-mode operation (cost vs quality)
- Complete edit history and reversibility
- Self-hosted with external AI API calls

All components are fully functional and ready for deployment.

docker-compose.dev.yml

@@ -0,0 +1,46 @@
+version: '3.8'
+
+services:
+  backend:
+    build:
+      context: ./backend
+      dockerfile: Dockerfile
+    container_name: ai-photo-edit-backend-dev
+    ports:
+      - "8000:8000"
+    volumes:
+      - ./data:/app/data
+      - ./backend:/app
+    environment:
+      - DATABASE_URL=sqlite:///./data/ai_photo_edit.db
+      - SECRET_KEY=dev-secret-key-change-in-production
+      - AI_PROVIDER=${AI_PROVIDER:-mock}
+      - OPENAI_API_KEY=${OPENAI_API_KEY:-}
+      - STABILITY_API_KEY=${STABILITY_API_KEY:-}
+      - CORS_ORIGINS=http://localhost:5173,http://localhost:3000,http://localhost
+    command: uvicorn app.main:app --host 0.0.0.0 --port 8000 --reload
+    restart: unless-stopped
+    networks:
+      - ai-photo-edit-network
+
+  frontend:
+    build:
+      context: ./frontend
+      dockerfile: Dockerfile.dev
+    container_name: ai-photo-edit-frontend-dev
+    ports:
+      - "5173:5173"
+    volumes:
+      - ./frontend:/app
+      - /app/node_modules
+    environment:
+      - VITE_API_BASE_URL=http://localhost:8000
+    depends_on:
+      - backend
+    restart: unless-stopped
+    networks:
+      - ai-photo-edit-network
+
+networks:
+  ai-photo-edit-network:
+    driver: bridge