ci(release): build releases with the Wails v3 toolchain

Release flow (make build -> build/bin/AniTrack -> tarball) is unchanged; only the toolchain moves to v3.

- Wails CLI: v2@v2.15.0 -> wails3@v3.0.0-beta.20 (binary path, cache key, and install pin updated together).
- System deps: libgtk-3-dev/libwebkit2gtk-4.1-dev -> libgtk-4-dev/libwebkitgtk-6.0-dev for the v3 default GTK4/WebKit 6.0 stack.
- Unchanged and still valid: Go/npm/go-build/Wails-CLI caches (npm cache now resolves since the frontend lockfile is committed), environment.go generation, version guard, idempotent release+asset upload.

.gitea/workflows/release.yml

@@ -106,9 +106,10 @@ jobs:
         run: |
           set -euo pipefail
           sudo apt-get update
+          # v3 desktop defaults to the GTK4/WebKitGTK 6.0 stack.
           sudo apt-get install -y \
             build-essential pkg-config \
-            libgtk-3-dev libwebkit2gtk-4.1-dev \
+            libgtk-4-dev libwebkitgtk-6.0-dev \
             jq
 
       - name: Cache Wails CLI
@@ -117,14 +118,14 @@ jobs:
         with:
           # The compiled CLI binary. Bump the key whenever the @version pin
           # below changes, or the old CLI will be silently reused.
-          path: ~/go/bin/wails
-          key: wails-v2.15.0-${{ runner.os }}
+          path: ~/go/bin/wails3
+          key: wails3-v3.0.0-beta.20-${{ runner.os }}
 
       - name: Install Wails CLI
         if: steps.wails-cli.outputs.cache-hit != 'true'
         run: |
           set -euo pipefail
-          go install github.com/wailsapp/wails/v2/cmd/wails@v2.15.0
+          go install github.com/wailsapp/wails/v3/cmd/wails3@v3.0.0-beta.20
 
       - name: Add Go bin to PATH
         run: echo "${HOME}/go/bin" >> "${GITHUB_PATH}"