feat: Phase 3 插件与工具系统 — Plugin SDK + Plugin Manager + 13内置插件 (40文件, 3293行)

- Plugin SDK: Plugin/Tool/ComplexTool/HostAPI 标准化接口
- Plugin Manager: 插件生命周期管理 (Install/Enable/Disable/Uninstall/Reload)
- Tool Registry: 聚合工具注册表 (Register/Execute/Dispatch)
- 13 个内置插件: 将原有硬编码工具迁移为标准插件格式
- REST API: 11 个端点 (net/http, 零外部依赖)
- ai-core 集成: PluginManagerClient 替代本地工具调用
- plugin.json 元数据: 每个插件含完整 author/version/category/permissions

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/plugin-manager/internal/sdk/permissions.go

@@ -0,0 +1,35 @@
+package sdk
+
+// PluginPermissions defines what a plugin is allowed to do.
+type PluginPermissions struct {
+	NetworkAllowed bool     `json:"networkAllowed"`
+	AllowedHosts   []string `json:"allowedHosts,omitempty"`
+	IoTRead        bool     `json:"iotRead"`
+	IoTWrite       bool     `json:"iotWrite"`
+	MemoryRead     bool     `json:"memoryRead"`
+	MemoryWrite    bool     `json:"memoryWrite"`
+	FileRead       bool     `json:"fileRead"`
+	FileWrite      bool     `json:"fileWrite"`
+	AllowedPaths   []string `json:"allowedPaths,omitempty"`
+	ExecAllowed    bool     `json:"execAllowed"`
+	MaxCPUPercent  float64  `json:"maxCPUPercent"`
+	MaxMemoryMB    int      `json:"maxMemoryMB"`
+}
+
+// DefaultPermissions returns a safe default permission set.
+func DefaultPermissions() PluginPermissions {
+	return PluginPermissions{
+		NetworkAllowed: false,
+		AllowedHosts:   []string{},
+		IoTRead:        false,
+		IoTWrite:       false,
+		MemoryRead:     false,
+		MemoryWrite:    false,
+		FileRead:       false,
+		FileWrite:      false,
+		AllowedPaths:   []string{},
+		ExecAllowed:    false,
+		MaxCPUPercent:  10.0,
+		MaxMemoryMB:    128,
+	}
+}