fix(ci): regenerate icon.ico with BMP-only entries

All six entries in the original icon.ico used PNG compression inside
the ICO container. Older versions of llvm-rc (used during Windows
cross-compilation) cannot parse PNG-compressed ICO entries, causing
the resource compilation step to fail since PR #1.

Regenerated with ImageMagick using -compress None to force BMP format
for all sizes including 256x256. Reverts the LLVM pinning attempts
as they are no longer needed.

.gitea/workflows/ci.yml

@@ -92,11 +92,10 @@ jobs:
             patchelf \
             libgtk-3-dev \
             libayatana-appindicator3-dev \
-            clang-18 \
-            lld-18 \
-            llvm-18 \
+            clang \
+            lld \
+            llvm \
             nsis
-          echo "/usr/lib/llvm-18/bin" >> $GITHUB_PATH
 
       - name: Setup pnpm
         uses: pnpm/action-setup@v4