fix(ci): add xcodegen project.yml and generate xcodeproj before archive

SPM executableTarget is treated as a CLI tool by xcodebuild, producing
Products/usr/local/bin instead of a .app bundle. xcodegen generates a
proper application target with PRODUCT_TYPE=com.apple.product-type.application.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

project.yml

@@ -0,0 +1,43 @@
+name: SilverApple
+options:
+  bundleIdPrefix: uk.silverlabs
+  deploymentTarget:
+    iOS: "16.0"
+  xcodeVersion: "15"
+  generateEmptyDirectories: true
+
+targets:
+  SilverApple:
+    type: application
+    platform: iOS
+    deploymentTarget: "16.0"
+    sources:
+      - path: SilverApple
+        excludes:
+          - Info.plist
+          - SilverApple.entitlements
+    resources:
+      - SilverApple/Assets.xcassets
+    settings:
+      base:
+        PRODUCT_BUNDLE_IDENTIFIER: uk.silverlabs.silverapple
+        INFOPLIST_FILE: SilverApple/Info.plist
+        CODE_SIGN_ENTITLEMENTS: SilverApple/SilverApple.entitlements
+        SWIFT_VERSION: "5.9"
+        TARGETED_DEVICE_FAMILY: "1,2"
+        OTHER_LDFLAGS:
+          - "-framework AuthenticationServices"
+          - "-framework SafariServices"
+          - "-framework Security"
+
+  SilverAppleTests:
+    type: bundle.unit-test
+    platform: iOS
+    deploymentTarget: "16.0"
+    sources:
+      - path: SilverAppleTests
+    dependencies:
+      - target: SilverApple
+    settings:
+      base:
+        SWIFT_VERSION: "5.9"