feat: add unified Settings sheet, MCP indicator, and Docker host config

- Add AppSettingsSheet (gear icon in Toolbar) with MCP, Docker, and AI sections
- MCP Server: toggle on/off, port config, status badge, endpoint URL with copy
- Docker: local/remote daemon selector with remote URL input
- AI: moved Ollama settings into the unified sheet
- MCP status probes actual TCP port for reliable running detection
- Docker commands respect configurable docker host (-H flag) for remote daemons
- MCP server supports graceful shutdown via tokio watch channel
- Settings persisted to app_settings.json alongside existing config files
- StatusBar shows MCP indicator (green/gray dot) with tooltip

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/types/index.ts

@@ -323,6 +323,30 @@ export interface ErdData {
   relationships: ErdRelationship[];
 }
 
+// App Settings
+export type DockerHost = "local" | "remote";
+
+export interface McpSettings {
+  enabled: boolean;
+  port: number;
+}
+
+export interface DockerSettings {
+  host: DockerHost;
+  remote_url?: string;
+}
+
+export interface AppSettings {
+  mcp: McpSettings;
+  docker: DockerSettings;
+}
+
+export interface McpStatus {
+  enabled: boolean;
+  port: number;
+  running: boolean;
+}
+
 // Docker
 export interface DockerStatus {
   installed: boolean;