feat(dictionary): add iCloud KVS sync, cloud ASR, and lexicon expansion

Mirror the personal dictionary through iCloud Key-Value Store with
deterministic merge rules, main-app-only sync UI, and App Group as the
keyboard runtime cache. Add cloud-engine ASR with dictionary bias and
expand the bundled custom language model lexicon.

OSGKeyboardShared/Services/PersonalDictionaryCloudSync/UbiquitousKeyValueStoreing.swift

@@ -0,0 +1,15 @@
+// UbiquitousKeyValueStoreing.swift
+// OSGKeyboard · Shared
+//
+// Test seam around `NSUbiquitousKeyValueStore`.
+
+import Foundation
+
+public protocol UbiquitousKeyValueStoreing: AnyObject {
+    func data(forKey key: String) -> Data?
+    func set(_ value: Data?, forKey key: String)
+    @discardableResult
+    func synchronize() -> Bool
+}
+
+extension NSUbiquitousKeyValueStore: UbiquitousKeyValueStoreing {}