feat: add multiple productivity features and UI enhancements (#68)

## Summary

This PR adds a collection of productivity features and UI enhancements to improve the Hikari Desktop experience:

### New Features
- **Clipboard History** (#25) - Track and manage copied code snippets with language detection, search, filtering, and pinning
- **Quick Actions Panel** (#15) - Buttons for common quick actions like "Review PR", "Run tests", "Explain file", with customizable actions
- **Git Integration Panel** (#24) - View current branch, changed/staged files, quick git actions (commit, push, pull), and branch management
- **Session Import/Export** (#8) - Export conversations to JSON and import previously saved sessions
- **Snippet Library** (#22) - Save and reuse common prompts with categories and quick insert
- **Session History** (#14) - Auto-save conversations with browsable history and search
- **High Contrast Mode** (#20) - Accessibility theme with improved visibility
- **Minimize to System Tray** (#11) - System tray support with right-click menu

### UI Enhancements
- Trans-pride gradient theme applied across UI elements
- Copy button added to code blocks
- Linter formatting and eslint-disable comments for cleaner code

## Closes

Closes #8
Closes #11
Closes #14
Closes #15
Closes #20
Closes #22
Closes #24
Closes #25
Closes #34
Closes #35
Closes #36
Closes #37
Closes #69
Closes #70

## Test Plan

- [ ] Verify clipboard history captures code from code block copy buttons
- [ ] Verify clipboard history captures manually selected text from terminal
- [ ] Test snippet library CRUD operations and insertion
- [ ] Test quick actions panel with default and custom actions
- [ ] Test git panel shows correct status, branch, and performs git operations
- [ ] Test session history auto-save and restore
- [ ] Test session import/export roundtrip
- [ ] Verify high contrast mode provides adequate contrast
- [ ] Test minimize to tray functionality and tray menu
- [ ] Verify trans-pride gradient theme displays correctly in all themes

---
*✨ This PR was created with help from Hikari~ 🌸*

Co-authored-by: Naomi Carrigan <commits@nhcarrigan.com>
Reviewed-on: #68
Co-authored-by: Hikari <hikari@nhcarrigan.com>
Co-committed-by: Hikari <hikari@nhcarrigan.com>

src-tauri/src/config.rs

@@ -70,6 +70,32 @@ pub struct HikariConfig {
 
     #[serde(default = "default_font_size")]
     pub font_size: u32,
+
+    #[serde(default)]
+    pub minimize_to_tray: bool,
+
+    #[serde(default)]
+    pub streamer_mode: bool,
+
+    #[serde(default)]
+    pub streamer_hide_paths: bool,
+
+    #[serde(default)]
+    pub compact_mode: bool,
+
+    // Profile fields
+    #[serde(default)]
+    pub profile_name: Option<String>,
+
+    #[serde(default)]
+    pub profile_avatar_path: Option<String>,
+
+    #[serde(default)]
+    pub profile_bio: Option<String>,
+
+    // Custom theme colors
+    #[serde(default)]
+    pub custom_theme_colors: CustomThemeColors,
 }
 
 impl Default for HikariConfig {
@@ -89,6 +115,14 @@ impl Default for HikariConfig {
             update_checks_enabled: true,
             character_panel_width: None,
             font_size: 14,
+            minimize_to_tray: false,
+            streamer_mode: false,
+            streamer_hide_paths: false,
+            compact_mode: false,
+            profile_name: None,
+            profile_avatar_path: None,
+            profile_bio: None,
+            custom_theme_colors: CustomThemeColors::default(),
         }
     }
 }
@@ -119,6 +153,29 @@ pub enum Theme {
     #[default]
     Dark,
     Light,
+    #[serde(rename = "high-contrast")]
+    HighContrast,
+    Custom,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, Default, PartialEq)]
+pub struct CustomThemeColors {
+    #[serde(default)]
+    pub bg_primary: Option<String>,
+    #[serde(default)]
+    pub bg_secondary: Option<String>,
+    #[serde(default)]
+    pub bg_terminal: Option<String>,
+    #[serde(default)]
+    pub accent_primary: Option<String>,
+    #[serde(default)]
+    pub accent_secondary: Option<String>,
+    #[serde(default)]
+    pub text_primary: Option<String>,
+    #[serde(default)]
+    pub text_secondary: Option<String>,
+    #[serde(default)]
+    pub border_color: Option<String>,
 }
 
 #[cfg(test)]
@@ -140,6 +197,14 @@ mod tests {
         assert!(config.update_checks_enabled);
         assert!(config.character_panel_width.is_none());
         assert_eq!(config.font_size, 14);
+        assert!(!config.minimize_to_tray);
+        assert!(!config.streamer_mode);
+        assert!(!config.streamer_hide_paths);
+        assert!(!config.compact_mode);
+        assert!(config.profile_name.is_none());
+        assert!(config.profile_avatar_path.is_none());
+        assert!(config.profile_bio.is_none());
+        assert_eq!(config.custom_theme_colors, CustomThemeColors::default());
     }
 
     #[test]
@@ -159,6 +224,14 @@ mod tests {
             update_checks_enabled: true,
             character_panel_width: Some(400),
             font_size: 16,
+            minimize_to_tray: true,
+            streamer_mode: false,
+            streamer_hide_paths: false,
+            compact_mode: false,
+            profile_name: Some("Test User".to_string()),
+            profile_avatar_path: None,
+            profile_bio: Some("A test bio".to_string()),
+            custom_theme_colors: CustomThemeColors::default(),
         };
 
         let json = serde_json::to_string(&config).unwrap();
@@ -179,8 +252,16 @@ mod tests {
     fn test_theme_serialization() {
         let dark = Theme::Dark;
         let light = Theme::Light;
+        let high_contrast = Theme::HighContrast;
 
         assert_eq!(serde_json::to_string(&dark).unwrap(), "\"dark\"");
         assert_eq!(serde_json::to_string(&light).unwrap(), "\"light\"");
+        assert_eq!(
+            serde_json::to_string(&high_contrast).unwrap(),
+            "\"high-contrast\""
+        );
+
+        let custom = Theme::Custom;
+        assert_eq!(serde_json::to_string(&custom).unwrap(), "\"custom\"");
     }
 }