Add Web Dashboard with multi-device control and callback hooks

Features:
- Web Dashboard: FastAPI-based dashboard with Vue.js frontend
  - Multi-device support (ADB, HDC, iOS)
  - Real-time WebSocket updates for task progress
  - Device management with status tracking
  - Task queue with execution controls (start/stop/re-execute)
  - Detailed task information display (thinking, actions, completion messages)
  - Screenshot viewing per device
  - LAN deployment support with configurable CORS

- Callback Hooks: Interrupt and modify task execution
  - step_callback: Called after each step with StepResult
  - before_action_callback: Called before executing action
  - Support for task interruption and dynamic task switching
  - Example scripts demonstrating callback usage

- Configuration: Environment-based configuration
  - .env file support for all settings
  - .env.example template with documentation
  - Model API configuration (base URL, model name, API key)
  - Dashboard configuration (host, port, CORS, device type)
  - Phone agent configuration (delays, max steps, language)

Technical improvements:
- Fixed forward reference issue with StepResult
- Added package exports for callback types and configs
- Enhanced dependencies with FastAPI, WebSocket support
- Thread-safe task execution with device locking
- Async WebSocket broadcasting from sync thread pool

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

dashboard/models/device.py

@@ -0,0 +1,67 @@
+"""
+Device data models for the dashboard.
+"""
+
+from datetime import datetime
+from enum import Enum
+from typing import Optional
+
+from pydantic import BaseModel, Field
+
+
+class DeviceType(str, Enum):
+    """Device connection type."""
+
+    ADB = "adb"
+    HDC = "hdc"
+    IOS = "ios"
+
+
+class DeviceStatus(str, Enum):
+    """Device status."""
+
+    ONLINE = "online"
+    OFFLINE = "offline"
+    BUSY = "busy"
+    ERROR = "error"
+
+
+class DeviceSchema(BaseModel):
+    """Device schema for API responses."""
+
+    device_id: str = Field(..., description="Unique device identifier")
+    status: DeviceStatus = Field(default=DeviceStatus.OFFLINE, description="Device status")
+    device_type: DeviceType = Field(..., description="Device connection type")
+    model: Optional[str] = Field(None, description="Device model name")
+    android_version: Optional[str] = Field(None, description="Android/iOS version")
+    current_app: Optional[str] = Field(None, description="Currently active app")
+    last_seen: datetime = Field(default_factory=datetime.now, description="Last connection time")
+    is_connected: bool = Field(True, description="Whether device is connected")
+    screenshot: Optional[str] = Field(None, description="Base64 encoded screenshot")
+
+    class Config:
+        json_schema_extra = {
+            "example": {
+                "device_id": "emulator-5554",
+                "status": "online",
+                "device_type": "adb",
+                "model": "sdk_gphone64_x86_64",
+                "android_version": "14",
+                "current_app": "com.android.launcher3",
+                "is_connected": True,
+            }
+        }
+
+
+class DeviceInfo(BaseModel):
+    """Extended device information."""
+
+    device_id: str
+    status: DeviceStatus
+    device_type: DeviceType
+    model: Optional[str] = None
+    android_version: Optional[str] = None
+    current_app: Optional[str] = None
+    last_seen: datetime
+    screenshot: Optional[str] = None
+    is_connected: bool = True