Improve: fix white scrollbar issue in Tauri dark theme

- Add color-scheme: dark meta tag and CSS for proper dark scrollbars
- Implement ultra-thin (3px) elegant scrollbars globally
- Remove overflow-hidden that was cutting scrollbar at top
- Clean up redundant scrollbar CSS and component styling
- Optimize scrollbar appearance for both web and Tauri desktop

Fixes scrollbar visibility issues in dark theme across all components.

bun.lock

@@ -44,6 +44,7 @@
         "tailwind-merge": "^2.6.0",
         "tailwindcss": "^4.1.8",
         "zod": "^3.24.1",
+        "zustand": "^5.0.6",
       },
       "devDependencies": {
         "@tauri-apps/cli": "^2",
@@ -1021,6 +1022,8 @@
 
     "zod": ["zod@3.25.67", "", {}, "sha512-idA2YXwpCdqUSKRCACDE6ItZD9TZzy3OZMtpfLoh6oPR47lipysRrJfjzMqFxQ3uJuUPyUeWe1r9vLH33xO/Qw=="],
 
+    "zustand": ["zustand@5.0.6", "", { "peerDependencies": { "@types/react": ">=18.0.0", "immer": ">=9.0.6", "react": ">=18.0.0", "use-sync-external-store": ">=1.2.0" }, "optionalPeers": ["@types/react", "immer", "react", "use-sync-external-store"] }, "sha512-ihAqNeUVhe0MAD+X8M5UzqyZ9k3FFZLBTtqo6JLPwV53cbRB/mJwBI0PxcIgqhBBHlEs8G45OTDTMq3gNcLq3A=="],
+
     "zwitch": ["zwitch@2.0.4", "", {}, "sha512-bXE4cR/kVZhKZX/RjPEflHaKVhUVl85noU3v6b8apfQEc1x4A+zBxjZ4lN8LqGd6WZ3dl98pY4o717VFmoPp+A=="],
 
     "@babel/core/semver": ["semver@6.3.1", "", { "bin": { "semver": "bin/semver.js" } }, "sha512-BR7VvDCVHO+q2xBEWskxS6DJE1qRnb7DxzUrogb71CWoSficBxYsiAGd+Kl0mmq/MprG9yArRkyrQxTO6XjMzA=="],