chore: remove CW decoder module (Morse Expert)

Removes the CW decoder entirely. The feature/cw module was a verbatim
decompilation of Morse Expert 1.15 (VE3NEA, a paid Play Store app),
shipped without licence or attribution, and restricted to the armeabi-v7a
ABI only -- which blocks Google Play distribution (64-bit required since
2019-08).

Deleted:
- feature/cw: 11,519 lines of obfuscated decompiled Java,
  libnativedecoderjni.so, layouts and resources
- core/domain/cw: 998 lines of unreachable Kotlin DSP plus its 300-line
  test (CwStartListening and friends were never dispatched by any UI)

Cleaned up in feature/radar:
- Removed CwDecoderPanel, CwSubState, CwStatus and 6 CW actions
- Removed the CW branches and decoder plumbing from RadarViewModel
- Dropped now-unused dependencies: :feature:cw, :feature:mutual (was
  declared but never imported), androidx.constraintlayout
- Removed radar_cw_* strings from en and zh

Kept deliberately: IAudioCapture, audioCapture and the RECORD_AUDIO
permission -- these are shared with SSTV and must not be removed.

CW decoding is gone until it is rewritten. See branch for the deleted
implementation if you need to reference it.

core/presentation/src/main/res/values-zh/strings.xml

@@ -99,11 +99,6 @@
     <string name="radar_doppler_offset_hint">偏移 (kHz)</string>
     <string name="radar_doppler_info">线性转发器：输入一个频率即可算出另一个</string>
 
-    <string name="radar_cw_decoder">CW 解码器</string>
-    <string name="radar_cw_start">开始</string>
-    <string name="radar_cw_stop">停止</string>
-    <string name="radar_cw_reset">清空</string>
-
     <!-- Map screen -->
     <string name="map_prev">上一个</string>
     <string name="map_next">下一个</string>

core/presentation/src/main/res/values/strings.xml

@@ -122,11 +122,6 @@
     <string name="radar_doppler_offset_hint">Offset (kHz)</string>
     <string name="radar_doppler_info">For linear transponders, type one frequency to see the other</string>
 
-    <string name="radar_cw_decoder">CW Decoder</string>
-    <string name="radar_cw_start">Start</string>
-    <string name="radar_cw_stop">Stop</string>
-    <string name="radar_cw_reset">Clear</string>
-
     <!-- Map screen -->
     <string name="map_prev">Prev</string>
     <string name="map_next">Next</string>