feat(engine): 添加 Vosk 本地离线引擎支持

- 新增 Vosk 引擎配置和识别逻辑
- 更新用户界面，增加 Vosk 引擎选项和模型路径设置
- 更新依赖，添加 vosk 库

caption-engine/main-vosk.spec

@@ -0,0 +1,42 @@
+# -*- mode: python ; coding: utf-8 -*-
+
+from pathlib import Path
+
+vosk_path = str(Path('./subenv/Lib/site-packages/vosk').resolve())
+
+a = Analysis(
+    ['main-vosk.py'],
+    pathex=[],
+    binaries=[],
+    datas=[(vosk_path, 'vosk')],
+    hiddenimports=[],
+    hookspath=[],
+    hooksconfig={},
+    runtime_hooks=[],
+    excludes=[],
+    noarchive=False,
+    optimize=0,
+)
+
+pyz = PYZ(a.pure)
+
+exe = EXE(
+    pyz,
+    a.scripts,
+    a.binaries,
+    a.datas,
+    [],
+    name='main-vosk',
+    debug=False,
+    bootloader_ignore_signals=False,
+    strip=False,
+    upx=True,
+    upx_exclude=[],
+    runtime_tmpdir=None,
+    console=True,
+    disable_windowed_traceback=False,
+    argv_emulation=False,
+    target_arch=None,
+    codesign_identity=None,
+    entitlements_file=None,
+)