feat(macos): local ASR model manager, menu-bar polish, and release 0.5.2

Adds a bundled local ASR model catalog for the macOS app with one-click
Sherpa Qwen3 / SenseVoice downloads (pause/resume, inline actions) and a
shared model storage directory used by MLX Qwen3. Fixes the light-mode
sidebar material and makes the menu-bar icon follow the system appearance
with a refreshed status mark. Renames the built product to OSGKeyboard.app.

Bumps version to 0.5.2 (build 19).

OSGKeyboardShared/Models/ProviderConfig.swift

@@ -74,7 +74,7 @@ public final class ProviderConfig: ObservableObject, @unchecked Sendable {
             guard !isApplyingConfiguration, engineMode != configuration.engineMode else { return }
             configuration.engineMode = engineMode
             applyEngineModeSideEffects()
-            persistConfiguration()
+            persistConfiguration(postConfigChanged: true)
         }
     }
     @Published public var hasCompletedOnboarding: Bool {