Fix mobile iOS Fastlane paths (#6004)

Co-authored-by: Orca <help@stably.ai>

mobile/fastlane/Fastfile

@@ -19,8 +19,12 @@ require "json"
 
 default_platform(:ios)
 
-APP_CONFIG_PATH = "app.json"
-WORKSPACE = "ios/Orca.xcworkspace"
+MOBILE_ROOT = File.expand_path("..", __dir__)
+# Why: fastlane executes lanes from mobile/fastlane even when GitHub Actions
+# starts in mobile/, so release file paths must be rooted at the mobile app.
+APP_CONFIG_PATH = File.join(MOBILE_ROOT, "app.json")
+WORKSPACE = File.join(MOBILE_ROOT, "ios", "Orca.xcworkspace")
+BUILD_OUTPUT_DIRECTORY = File.join(MOBILE_ROOT, "build")
 SCHEME = "Orca"
 BUNDLE_ID = "com.stably.orca.mobile"
 TESTFLIGHT_GROUPS = ["peeps"].freeze
@@ -126,7 +130,7 @@ platform :ios do
           BUNDLE_ID => profile_name,
         },
       },
-      output_directory: "build",
+      output_directory: BUILD_OUTPUT_DIRECTORY,
       output_name: "Orca.ipa",
       clean: true,
     )