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-tauri/src/commands/settings.rs

@@ -0,0 +1,116 @@
+use crate::error::{TuskError, TuskResult};
+use crate::mcp;
+use crate::models::settings::{AppSettings, DockerHost, McpStatus};
+use crate::state::AppState;
+use std::fs;
+use std::sync::Arc;
+use tauri::{AppHandle, Manager, State};
+
+fn get_settings_path(app: &AppHandle) -> TuskResult<std::path::PathBuf> {
+    let dir = app
+        .path()
+        .app_data_dir()
+        .map_err(|e| TuskError::Custom(e.to_string()))?;
+    fs::create_dir_all(&dir)?;
+    Ok(dir.join("app_settings.json"))
+}
+
+#[tauri::command]
+pub async fn get_app_settings(app: AppHandle) -> TuskResult<AppSettings> {
+    let path = get_settings_path(&app)?;
+    if !path.exists() {
+        return Ok(AppSettings::default());
+    }
+    let data = fs::read_to_string(&path)?;
+    let settings: AppSettings = serde_json::from_str(&data)?;
+    Ok(settings)
+}
+
+#[tauri::command]
+pub async fn save_app_settings(
+    app: AppHandle,
+    state: State<'_, Arc<AppState>>,
+    settings: AppSettings,
+) -> TuskResult<()> {
+    let path = get_settings_path(&app)?;
+    let data = serde_json::to_string_pretty(&settings)?;
+    fs::write(&path, data)?;
+
+    // Apply docker host setting
+    {
+        let mut docker_host = state.docker_host.write().await;
+        *docker_host = match settings.docker.host {
+            DockerHost::Remote => settings.docker.remote_url.clone(),
+            DockerHost::Local => None,
+        };
+    }
+
+    // Apply MCP setting: restart or stop
+    let is_running = *state.mcp_running.read().await;
+
+    if settings.mcp.enabled {
+        if is_running {
+            // Stop existing MCP server first
+            let _ = state.mcp_shutdown_tx.send(true);
+            // Give it a moment to shut down
+            tokio::time::sleep(std::time::Duration::from_millis(200)).await;
+            *state.mcp_running.write().await = false;
+        }
+
+        // Start new MCP server
+        let connections_path = app
+            .path()
+            .app_data_dir()
+            .map_err(|e| TuskError::Custom(e.to_string()))?
+            .join("connections.json");
+
+        let mcp_state = state.inner().clone();
+        let port = settings.mcp.port;
+        let shutdown_rx = state.mcp_shutdown_tx.subscribe();
+
+        tokio::spawn(async move {
+            *mcp_state.mcp_running.write().await = true;
+            if let Err(e) =
+                mcp::start_mcp_server(mcp_state.clone(), connections_path, port, shutdown_rx).await
+            {
+                log::error!("MCP server error: {}", e);
+            }
+            *mcp_state.mcp_running.write().await = false;
+        });
+    } else if is_running {
+        // Stop MCP server
+        let _ = state.mcp_shutdown_tx.send(true);
+        *state.mcp_running.write().await = false;
+    }
+
+    Ok(())
+}
+
+#[tauri::command]
+pub async fn get_mcp_status(app: AppHandle) -> TuskResult<McpStatus> {
+    // Read settings from file for enabled/port
+    let settings = {
+        let path = get_settings_path(&app)?;
+        if path.exists() {
+            let data = fs::read_to_string(&path)?;
+            serde_json::from_str::<AppSettings>(&data).unwrap_or_default()
+        } else {
+            AppSettings::default()
+        }
+    };
+
+    // Probe the actual port to determine if MCP is running
+    let running = tokio::time::timeout(
+        std::time::Duration::from_millis(500),
+        tokio::net::TcpStream::connect(format!("127.0.0.1:{}", settings.mcp.port)),
+    )
+    .await
+    .map(|r| r.is_ok())
+    .unwrap_or(false);
+
+    Ok(McpStatus {
+        enabled: settings.mcp.enabled,
+        port: settings.mcp.port,
+        running,
+    })
+}