feat: Major UI improvements and SSH-only mode

- Tool rendering: Unified tool_use/tool_result cards with collapsible results
- Special rendering for WebSearch, WebFetch, Task, Write tools
- File upload support with drag & drop
- Permission dialog for tool approvals
- Status bar with session stats and permission mode toggle
- SSH-only mode: Removed local container execution
- Host switching disabled during active session with visual indicator
- Directory browser: Browse remote directories via SSH
- Recent directories dropdown with localStorage persistence
- Follow-up messages during generation
- Improved scroll behavior with "back to bottom" button

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/Dockerfile.dev

@@ -0,0 +1,15 @@
+FROM node:20-slim
+
+WORKDIR /app
+
+# Copy package files
+COPY package*.json ./
+
+# Install dependencies
+RUN npm install
+
+# Expose Vite port
+EXPOSE 5173
+
+# Start Vite dev server
+CMD ["npx", "vite", "--host", "0.0.0.0", "--port", "5173"]