ci: use assetNamePattern for stable download URLs

Replace copy/upload hack with tauri-action's built-in
assetNamePattern: "SidStack-[arch][ext]" to produce
version-free filenames (SidStack-aarch64.dmg, SidStack-x64.dmg).

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: Dchuong03

.github/workflows/release.yml

@@ -55,16 +55,4 @@ jobs:
           releaseDraft: true
           prerelease: false
           args: --target ${{ matrix.target }}
-
-      - name: Upload fixed-name DMG
-        run: |
-          DMG_FILE=$(find src-tauri/target/${{ matrix.target }}/release/bundle/dmg -name "*.dmg" | head -1)
-          if [[ "${{ matrix.target }}" == "aarch64-apple-darwin" ]]; then
-            FIXED_NAME="SidStack_aarch64.dmg"
-          else
-            FIXED_NAME="SidStack_x64.dmg"
-          fi
-          cp "$DMG_FILE" "$FIXED_NAME"
-          gh release upload "${{ github.ref_name }}" "$FIXED_NAME" --clobber
-        env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          assetNamePattern: "SidStack-[arch][ext]"