feat(ios): port the Android client to SwiftUI

The iOS client is now a screen-for-screen port of the Android app over the
same pstr-android UniFFI surface, with no Rust changes: Library, title page,
History, Shares (public links and Drive folders), Downloads and Settings,
with the same strings, undo snackbars and two-pane layout on wide screens.

- Theme from the engine's palette (Material role names, Inter, the same
  type ramp and corners), repainted live from the appearance settings.
- Account sign-in with two-factor code, mailbox password and the Proton
  CAPTCHA in a non-persistent WKWebView, the Drive folder browser, and
  watch-history sync every five minutes, after sign-in, on player close and
  when the app leaves the screen.
- Player over libmpv: resume, progress saved every 5 s, autoplay with the
  up-next card, skip and auto-skip from the chapter plan, track, speed,
  volume and episode pickers, landscape lock, mini transport, and
  lock-screen controls with interruption and route-change handling.
- Offline downloads with the Android record format, free-space floor,
  retries, transfer rate and the Wi-Fi-only policy; interrupted transfers
  resume at next launch.
- Config, data and download state are excluded from backup, as Android's
  allowBackup=false: a restore would bring shares back without their
  Keychain secrets and give two devices one sync identity.

Picture-in-picture, the share sheet and background downloads are not
possible the same way on iOS; docs/IOS.md lists why and what replaces them.

Adds XCTest ports of the Android unit tests, a `test` command to
scripts/build-ios.sh, the app icon and its render script, and an iOS
workflow on macos-15 that runs the tests and builds the unsigned .ipa.

ios/project.yml

@@ -17,8 +17,24 @@ targets:
     platform: iOS
     sources:
       - path: ProtonStream
+        excludes:
+          # The icon's source; the asset catalog holds what it renders to.
+          - Resources/AppIcon.svg
+          - Resources/THIRD_PARTY_NOTICES.md
+      - path: ProtonStream/Resources/THIRD_PARTY_NOTICES.md
+        buildPhase: resources
       # UniFFI output, written by `scripts/build-ios.sh bindings`.
       - path: build/generated/PstrBridge.swift
+      # Shared with the Android client rather than copied: Inter, and the
+      # licence texts the About page shows.
+      - path: ../android/app/src/main/res/font/inter_regular.ttf
+        buildPhase: resources
+      - path: ../android/app/src/main/res/font/inter_semibold.ttf
+        buildPhase: resources
+      - path: ../android/app/src/main/assets/licenses/GPL-3.0.txt
+        buildPhase: resources
+      - path: ../android/app/src/main/assets/licenses/Inter-OFL.txt
+        buildPhase: resources
     dependencies:
       # The GPL build is the one with libass and every demuxer; the app is
       # sideloaded, never distributed through the App Store.
@@ -26,6 +42,9 @@ targets:
         product: MPVKit-GPL
       - sdk: Security.framework
       - sdk: SystemConfiguration.framework
+    scheme:
+      testTargets:
+        - ProtonStreamTests
     settings:
       base:
         PRODUCT_BUNDLE_IDENTIFIER: io.narl.protonstream
@@ -33,9 +52,11 @@ targets:
         CURRENT_PROJECT_VERSION: ${PSTR_BUILD}
         SWIFT_VERSION: "5.0"
         TARGETED_DEVICE_FAMILY: "1,2"
+        ASSETCATALOG_COMPILER_APPICON_NAME: AppIcon
         SWIFT_OBJC_BRIDGING_HEADER: ProtonStream/Bridge/ProtonStream-Bridging-Header.h
         HEADER_SEARCH_PATHS: $(PROJECT_DIR)/build/generated
-        LIBRARY_SEARCH_PATHS: $(PROJECT_DIR)/../target/aarch64-apple-ios/release
+        "LIBRARY_SEARCH_PATHS[sdk=iphoneos*]": $(PROJECT_DIR)/../target/aarch64-apple-ios/release
+        "LIBRARY_SEARCH_PATHS[sdk=iphonesimulator*]": $(PROJECT_DIR)/../target/aarch64-apple-ios-sim/release
         OTHER_LDFLAGS: -lpstr_android
     info:
       path: ProtonStream/Info.plist
@@ -44,8 +65,18 @@ targets:
         LSRequiresIPhoneOS: true
         ITSAppUsesNonExemptEncryption: false
         UIBackgroundModes: [audio]
-        UILaunchScreen: {}
+        # The Proton palette's page colour, so a dark app does not open on white.
+        UILaunchScreen:
+          UIColorName: LaunchBackground
         UIRequiresFullScreen: false
+        UIAppFonts:
+          - inter_regular.ttf
+          - inter_semibold.ttf
+        # A share link handed over from elsewhere: protonstream://add?url=…,
+        # or the link with its scheme swapped (IncomingShareLink.swift).
+        CFBundleURLTypes:
+          - CFBundleURLName: io.narl.protonstream.share-link
+            CFBundleURLSchemes: [protonstream]
         UISupportedInterfaceOrientations:
           - UIInterfaceOrientationPortrait
           - UIInterfaceOrientationLandscapeLeft
@@ -55,3 +86,17 @@ targets:
           - UIInterfaceOrientationPortraitUpsideDown
           - UIInterfaceOrientationLandscapeLeft
           - UIInterfaceOrientationLandscapeRight
+
+  # The pure logic the Android unit tests pin, pinned again here: hosted in the
+  # app, so `@testable import` reaches it, on the simulator.
+  ProtonStreamTests:
+    type: bundle.unit-test
+    platform: iOS
+    sources:
+      - path: ProtonStreamTests
+    dependencies:
+      - target: ProtonStream
+    settings:
+      base:
+        SWIFT_VERSION: "5.0"
+        GENERATE_INFOPLIST_FILE: YES