feat(ui): add dashboard sections with sidebar navigation and mock views

Add seven sidebar sections (Dashboard, Providers, Chat, Tools,
Knowledge Base, Developer, Organization) with fully rendered mock views,
nested sub-shells for Developer and Organization, and SearXNG container
for future news feed integration. Replaces the previous OverviewPage
with a news feed dashboard.

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

src/models/tool.rs

@@ -0,0 +1,73 @@
+use serde::{Deserialize, Serialize};
+
+/// Category grouping for MCP tools.
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+pub enum ToolCategory {
+    /// Web search and browsing tools
+    Search,
+    /// File and document processing tools
+    FileSystem,
+    /// Computation and math tools
+    Compute,
+    /// Code execution and analysis tools
+    Code,
+    /// Communication and notification tools
+    Communication,
+}
+
+impl ToolCategory {
+    /// Returns the display label for a tool category.
+    pub fn label(&self) -> &'static str {
+        match self {
+            Self::Search => "Search",
+            Self::FileSystem => "File System",
+            Self::Compute => "Compute",
+            Self::Code => "Code",
+            Self::Communication => "Communication",
+        }
+    }
+}
+
+/// Status of an MCP tool instance.
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+pub enum ToolStatus {
+    /// Tool is running and available
+    Active,
+    /// Tool is installed but not running
+    Inactive,
+    /// Tool encountered an error
+    Error,
+}
+
+impl ToolStatus {
+    /// Returns the CSS class suffix for status styling.
+    pub fn css_class(&self) -> &'static str {
+        match self {
+            Self::Active => "active",
+            Self::Inactive => "inactive",
+            Self::Error => "error",
+        }
+    }
+}
+
+/// An MCP (Model Context Protocol) tool entry.
+///
+/// # Fields
+///
+/// * `id` - Unique tool identifier
+/// * `name` - Human-readable display name
+/// * `description` - Brief description of what the tool does
+/// * `category` - Classification category
+/// * `status` - Current running status
+/// * `enabled` - Whether the tool is toggled on by the user
+/// * `icon` - Icon identifier for rendering
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+pub struct McpTool {
+    pub id: String,
+    pub name: String,
+    pub description: String,
+    pub category: ToolCategory,
+    pub status: ToolStatus,
+    pub enabled: bool,
+    pub icon: String,
+}