iOS: native upload and download services (background URLSession)

Swift implementation of the upload_service/download_service channels:
background PUT/GET against the account's WebDAV root, one summary local
notification per batch, Downloads visible in the Files app. Pure helpers
covered by RunnerTests.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

ios/RunnerTests/RunnerTests.swift

@@ -2,11 +2,51 @@ import Flutter
 import UIKit
 import XCTest
 
+@testable import Runner
+
 class RunnerTests: XCTestCase {
 
-  func testExample() {
-    // If you add code to the Runner application, consider adding tests here.
-    // See https://developer.apple.com/documentation/xctest for more information about using XCTest.
+  func testFileURLEncodesEachSegment() {
+    let url = WebDAV.fileURL(
+      serverUrl: "https://cloud.example.com", username: "alice",
+      remotePath: "/Tax Forms/2026 #1/a&b.pdf")
+    XCTAssertEqual(
+      url?.absoluteString,
+      "https://cloud.example.com/remote.php/dav/files/alice/Tax%20Forms/2026%20%231/a&b.pdf")
   }
 
+  func testFileURLKeepsServerSubPathAndDropsTrailingSlash() {
+    let url = WebDAV.fileURL(
+      serverUrl: "https://example.com/nextcloud/", username: "bob@home", remotePath: "docs/x.txt")
+    XCTAssertEqual(
+      url?.absoluteString,
+      "https://example.com/nextcloud/remote.php/dav/files/bob@home/docs/x.txt")
+  }
+
+  func testFileURLForRoot() {
+    XCTAssertEqual(
+      WebDAV.fileURL(serverUrl: "https://c.io", username: "u", remotePath: "/")?.absoluteString,
+      "https://c.io/remote.php/dav/files/u")
+  }
+
+  func testJoinUsesOneSlash() {
+    XCTAssertEqual(WebDAV.join("/", "a.txt"), "/a.txt")
+    XCTAssertEqual(WebDAV.join("/docs", "a.txt"), "/docs/a.txt")
+    XCTAssertEqual(WebDAV.join("/docs/", "a.txt"), "/docs/a.txt")
+  }
+
+  func testUniqueURLNumbersCollisions() throws {
+    let dir = FileManager.default.temporaryDirectory
+      .appendingPathComponent("noo-tests-\(UUID().uuidString)", isDirectory: true)
+    try FileManager.default.createDirectory(at: dir, withIntermediateDirectories: true)
+    defer { try? FileManager.default.removeItem(at: dir) }
+
+    XCTAssertEqual(LocalFiles.uniqueURL(in: dir, name: "a.txt").lastPathComponent, "a.txt")
+    FileManager.default.createFile(atPath: dir.appendingPathComponent("a.txt").path, contents: nil)
+    XCTAssertEqual(LocalFiles.uniqueURL(in: dir, name: "a.txt").lastPathComponent, "a (1).txt")
+    FileManager.default.createFile(atPath: dir.appendingPathComponent("a (1).txt").path, contents: nil)
+    XCTAssertEqual(LocalFiles.uniqueURL(in: dir, name: "a.txt").lastPathComponent, "a (2).txt")
+    FileManager.default.createFile(atPath: dir.appendingPathComponent("README").path, contents: nil)
+    XCTAssertEqual(LocalFiles.uniqueURL(in: dir, name: "README").lastPathComponent, "README (1)")
+  }
 }