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/wsl_bridge.rs

@@ -112,7 +112,7 @@ impl WslBridge {
             return Err("Process already running".to_string());
         }
 
-        // Load saved achievements when starting a new session
+        // Load saved achievements and stats when starting a new session
         let app_clone = app.clone();
         let stats = self.stats.clone();
         tauri::async_runtime::spawn(async move {
@@ -122,7 +122,17 @@ impl WslBridge {
                 "Loaded {} unlocked achievements",
                 achievements.unlocked.len()
             );
-            stats.write().achievements = achievements;
+
+            println!("Loading saved stats...");
+            let persisted_stats = crate::stats::load_stats(&app_clone).await;
+
+            let mut stats_guard = stats.write();
+            stats_guard.achievements = achievements;
+
+            if let Some(persisted) = persisted_stats {
+                println!("Applying persisted lifetime stats");
+                stats_guard.apply_persisted(persisted);
+            }
         });
 
         let working_dir = &options.working_dir;
@@ -440,6 +450,18 @@ impl WslBridge {
         self.session_id = None;
         self.mcp_config_file = None; // Temp file is automatically deleted when dropped
 
+        // Save lifetime stats before resetting session
+        let stats_snapshot = self.stats.read().clone();
+        let app_clone = app.clone();
+        tauri::async_runtime::spawn(async move {
+            println!("Saving stats on session stop...");
+            if let Err(e) = crate::stats::save_stats(&app_clone, &stats_snapshot).await {
+                eprintln!("Failed to save stats: {}", e);
+            } else {
+                println!("Stats saved successfully on session stop");
+            }
+        });
+
         // Reset session stats on explicit disconnect
         self.stats.write().reset_session();
 
@@ -733,10 +755,23 @@ fn process_json_line(
 
             let current_stats = stats.read().clone();
             let stats_event = StatsUpdateEvent {
-                stats: current_stats,
+                stats: current_stats.clone(),
             };
             let _ = app.emit("claude:stats", stats_event);
 
+            // Save stats periodically (every 10 messages to avoid excessive disk writes)
+            if current_stats.session_messages_exchanged.is_multiple_of(10)
+                && current_stats.session_messages_exchanged > 0
+            {
+                let app_handle = app.clone();
+                tauri::async_runtime::spawn(async move {
+                    println!("Periodic stats save (every 10 messages)...");
+                    if let Err(e) = crate::stats::save_stats(&app_handle, &current_stats).await {
+                        eprintln!("Failed to save stats: {}", e);
+                    }
+                });
+            }
+
             // Only emit error results - success content is already sent via Assistant message
             if subtype != "success" {
                 if let Some(text) = result {