style(FileHistoryPanel): enhance loading animation and styles

This update improves the loading animation for the File History Panel,
making it more visually appealing and responsive. The CSS has been
refactored to introduce new styles and animations, while the Svelte
component has been updated to utilize these changes effectively.

- Added new loading animations and styles for better user experience
- Refactored CSS to improve maintainability and visual design
- Updated Svelte component to integrate new loading elements

src/lib/components/FileHistoryPanel.svelte

@@ -1,5 +1,6 @@
 <script lang="ts">
   import { GitCompare, History, RotateCcw } from "@lucide/svelte";
+  import iconUrl from "../../../src-tauri/icons/icon.png";
   import type { GitCommit } from "../types";
 
   interface Props {
@@ -93,22 +94,17 @@
     <div class="blank-state">Select a file in Explorer.</div>
   {:else if isLoading}
     <div class="file-history-loading" role="status" aria-live="polite">
-      <svg class="file-history-loading-graph" viewBox="0 0 120 120" aria-hidden="true">
-        <defs>
-          <linearGradient id="fhl-line" x1="0" y1="0" x2="1" y2="1">
-            <stop offset="0%" stop-color="#646cff" />
-            <stop offset="100%" stop-color="#41d1ff" />
-          </linearGradient>
-        </defs>
-        <circle class="fhl-ring" cx="60" cy="60" r="52" />
-        <path class="fhl-trunk" d="M42 22 L42 98" />
-        <path class="fhl-branch" d="M42 44 C42 62, 82 58, 82 76 L82 88" />
-        <circle class="fhl-node fhl-n1" cx="42" cy="30" r="6" />
-        <circle class="fhl-node fhl-n2" cx="42" cy="60" r="6" />
-        <circle class="fhl-node fhl-n3" cx="82" cy="88" r="6" />
-        <circle class="fhl-node fhl-n4" cx="42" cy="90" r="6" />
-      </svg>
+      <div class="file-history-loading-mark" aria-hidden="true">
+        <span class="file-history-loading-halo"></span>
+        <svg class="file-history-loading-traces" viewBox="0 0 120 120">
+          <path class="fhl-trace fhl-trace-main" d="M14 82 C38 60, 48 58, 60 60 S84 66, 106 36" />
+          <path class="fhl-trace fhl-trace-branch" d="M28 36 C52 48, 70 70, 91 94" />
+        </svg>
+        <img src={iconUrl} alt="" class="file-history-loading-icon" />
+        <span class="file-history-loading-sheen"></span>
+      </div>
       <span class="file-history-loading-label">Loading history…</span>
+      <span class="file-history-loading-bar" aria-hidden="true"><span></span></span>
     </div>
   {:else if fileHistory.length === 0}
     <div class="blank-state">No history returned for this selection.</div>