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/lib/components/AnimeGirl.svelte

@@ -34,35 +34,12 @@
         return "animate-idle";
     }
   }
-
-  function getBackgroundGlow(): string {
-    switch (currentState) {
-      case "thinking":
-        return "shadow-thinking";
-      case "typing":
-        return "shadow-typing";
-      case "searching":
-        return "shadow-searching";
-      case "coding":
-        return "shadow-coding";
-      case "mcp":
-        return "shadow-mcp";
-      case "success":
-        return "shadow-success";
-      case "error":
-        return "shadow-error";
-      default:
-        return "";
-    }
-  }
 </script>
 
 <div
   class="anime-girl-container flex flex-col items-center justify-between h-full p-4 overflow-hidden"
 >
-  <div
-    class="character-frame relative {getBackgroundGlow()} flex-1 flex items-center justify-center min-h-0"
-  >
+  <div class="character-frame relative flex-1 flex items-center justify-center min-h-0">
     <div class="sprite-container {getAnimationClass()} h-full flex items-center justify-center">
       <img
         src="/sprites/{info.spriteFile}"
@@ -97,37 +74,12 @@
 </div>
 
 <style>
+  .anime-girl-container {
+    transition: all 0.3s ease;
+  }
+
   .character-frame {
-    border-radius: 50%;
-    transition: box-shadow 0.3s ease;
-  }
-
-  .shadow-thinking {
-    box-shadow: 0 0 30px rgba(147, 51, 234, 0.5);
-  }
-
-  .shadow-typing {
-    box-shadow: 0 0 30px rgba(59, 130, 246, 0.5);
-  }
-
-  .shadow-searching {
-    box-shadow: 0 0 30px rgba(234, 179, 8, 0.5);
-  }
-
-  .shadow-coding {
-    box-shadow: 0 0 30px rgba(34, 197, 94, 0.5);
-  }
-
-  .shadow-mcp {
-    box-shadow: 0 0 30px rgba(236, 72, 153, 0.5);
-  }
-
-  .shadow-success {
-    box-shadow: 0 0 30px rgba(16, 185, 129, 0.5);
-  }
-
-  .shadow-error {
-    box-shadow: 0 0 30px rgba(239, 68, 68, 0.5);
+    transition: all 0.3s ease;
   }
 
   @keyframes idle-bob {