MediaCodec (C2NodeImpl) leak on USB camera detach/reattach cycle

[cytew]

Description:

• Library version: 1.0.12
• Pattern: Each USB camera detach → reattach cycle leaks ~3 C2NodeImpl (Codec2 framework component nodes) that remain alive until app process termination.
• Tested on Samsung devices (Android 14)
• Perfetto trace shows the codec threads created at the time of camera
  initialization persist beyond device detach.

Reproduction:

1. Connect USB UVC camera
2. Start preview / open camera
3. Detach USB
4. Reattach USB
5. Repeat → C2NodeImpl count grows linearly

Expected: codec instances released on camera close/USB detach
Actual: codec instances persist; ~3 per cycle accumulated

Note: This is distinct from the image cache leak fixed in #125 (1.0.11).
That fix recycled UVC raw frame buffers in UVCPreview.cpp, but C2NodeImpl
instances (Android Codec2 framework) remain leaked.