fix: HackRF users get misleading RTL-SDR error in rtlamr/sstv/weather-sat modes

Several modes didn't pass sdr_type to claim_sdr_device(), defaulting to
'rtlsdr' and triggering an rtl_test USB probe that fails for HackRF with
a confusing "check that the RTL-SDR is connected" message.

- Add sdr_type to frontend start requests for rtlamr, weather-sat, sstv-general
- Read sdr_type in backend routes and pass to claim/release_sdr_device()
- Add early guard returning clear "not yet supported" error for non-RTL-SDR
  hardware in modes that are hardcoded to RTL-SDR tools
- Make probe_rtlsdr_device error message device-type-agnostic

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

utils/sdr/detection.py

@@ -493,7 +493,7 @@ def probe_rtlsdr_device(device_index: int) -> str | None:
             )
             return (
                 f'SDR device {device_index} is not available — '
-                f'check that the RTL-SDR is connected and not in use by another process.'
+                f'check that the SDR device is connected and not in use by another process.'
             )
 
     except Exception as e: