Add GitHub-style code preview + UE icon in context menu

- New CodeView: syntax-highlighted source (highlight.js, bundled offline)
  with line numbers for new files, colored unified diff for edits. Covers
  cpp/c/h, cs, py, js/ts, json/uproject, xml, ini, glsl. hljs tokens mapped
  to the app palette so it's theme-aware. Replaces the bare DiffView.
- Context-menu items now support icons; the Launch Unreal Engine item shows
  the UE mark.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

package-lock.json

@@ -1,18 +1,19 @@
 {
   "name": "exbyte-depot",
-  "version": "0.1.0",
+  "version": "0.2.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "exbyte-depot",
-      "version": "0.1.0",
+      "version": "0.2.0",
       "dependencies": {
         "@tauri-apps/api": "^2",
         "@tauri-apps/plugin-dialog": "^2.7.1",
         "@tauri-apps/plugin-opener": "^2",
         "@tauri-apps/plugin-process": "^2.3.1",
         "@tauri-apps/plugin-updater": "^2.10.1",
+        "highlight.js": "^11.11.1",
         "react": "^19.1.0",
         "react-dom": "^19.1.0",
         "three": "^0.185.1"
@@ -1820,6 +1821,15 @@
         "node": ">=6.9.0"
       }
     },
+    "node_modules/highlight.js": {
+      "version": "11.11.1",
+      "resolved": "https://registry.npmjs.org/highlight.js/-/highlight.js-11.11.1.tgz",
+      "integrity": "sha512-Xwwo44whKBVCYoliBQwaPvtd/2tYFkRQtXDWj1nackaV2JPXx3L0+Jvd8/qCJ2p+ML0/XVkJ2q+Mr+UVdpJK5w==",
+      "license": "BSD-3-Clause",
+      "engines": {
+        "node": ">=12.0.0"
+      }
+    },
     "node_modules/js-tokens": {
       "version": "4.0.0",
       "resolved": "https://registry.npmjs.org/js-tokens/-/js-tokens-4.0.0.tgz",