[ci-bitrise] Add Bitrise pipeline for TestFlight and App Store deploys

Modeled on LC Wallet's bitrise.yml. Push-only trigger map (develop->beta,
main->release), no PR-triggered checks. Reuses the existing Skip fastlane
lanes directly instead of a generic xcode-archive step, since build_app
already carries the Skip-specific xcconfig and build flags. Adds a beta
lane (TestFlight) to match release, which was the only lane wired before.

Darwin/fastlane/Fastfile

@@ -19,6 +19,19 @@ lane :assemble do |options|
   )
 end
 
+lane :beta do |options|
+  desc "Build and upload to TestFlight"
+
+  get_provisioning_profile(api_key_path: "fastlane/apikey.json")
+
+  assemble
+
+  upload_to_testflight(
+    api_key_path: "fastlane/apikey.json",
+    skip_waiting_for_build_processing: true
+  )
+end
+
 lane :release do |options|
   desc "Build and release app"