Add SAM Smart Select and AI Inpaint tools to miniPaint

New features:
- Smart Select tool: Click to select objects using SAM (Segment Anything)
- AI Inpaint tool: Edit selected regions with text prompts

Changes:
- frontend/src/js/tools/smart_select.js: SAM-powered selection tool
- frontend/src/js/tools/ai_inpaint.js: AI inpainting with prompt dialog
- frontend/src/js/services/api.js: API service for backend communication
- frontend/src/js/config.js: Register new tools
- frontend/src/css/layout.css: Tool icon styles
- frontend/images/icons/: SVG icons for new tools
- backend/app/routers/tools.py: New base64 API endpoints
- frontend/Dockerfile: Updated for miniPaint build
- frontend/nginx.conf: Added /api prefix proxy

frontend/Dockerfile

@@ -3,22 +3,25 @@ FROM node:20-alpine as build
 WORKDIR /app
 
 # Copy package files
-COPY package.json ./
+COPY package.json package-lock.json ./
 
 # Install dependencies
-RUN npm install
+RUN npm ci
 
 # Copy source
 COPY . .
 
-# Build app
+# Build webpack bundle
 RUN npm run build
 
 # Production stage
 FROM nginx:alpine
 
-# Copy built files
-COPY --from=build /app/dist /usr/share/nginx/html
+# Copy all static files needed by miniPaint
+COPY --from=build /app/index.html /usr/share/nginx/html/
+COPY --from=build /app/dist /usr/share/nginx/html/dist
+COPY --from=build /app/images /usr/share/nginx/html/images
+COPY --from=build /app/src/css /usr/share/nginx/html/src/css
 
 # Copy nginx config
 COPY nginx.conf /etc/nginx/conf.d/default.conf