fix: build_release.sh now passes Config.xcconfig to xcodebuild

The Release build wasn't picking up FEISHU_APP_ID / FEISHU_APP_SECRET
because xcodebuild doesn't automatically use Config.xcconfig unless
it's passed with -xcconfig flag. Added auto-detection: if Config.xcconfig
exists, it's used; otherwise a warning is printed.

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

scripts/build_release.sh

@@ -13,10 +13,20 @@ APP_NAME="Bugger.app"
 echo "=== Cleaning ==="
 xcodebuild -project "$PROJECT" -scheme "$SCHEME" clean 1>/dev/null
 
+# Use Config.xcconfig if present
+XCCONFIG_FLAG=""
+if [ -f "Config.xcconfig" ]; then
+    XCCONFIG_FLAG="-xcconfig Config.xcconfig"
+    echo "=== Using Config.xcconfig ==="
+else
+    echo "=== WARNING: Config.xcconfig not found, credentials will be empty ==="
+fi
+
 echo "=== Building Release ==="
 xcodebuild -project "$PROJECT" -scheme "$SCHEME" \
     -configuration Release \
     -derivedDataPath "$BUILD_DIR/derived" \
+    $XCCONFIG_FLAG \
     build 2>&1 | grep -E "^.../|error:|BUILD|warning:.*Swift"
 
 # Find the built .app