Remove waterfall from all modes except listening post

Reverts IQ pipeline and removes syncWaterfallToFrequency calls from
pager, sensor, rtlamr, DMR, SSTV, and SSTV general modes. Waterfall
is now exclusive to listening post mode.

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

app.py

@@ -232,13 +232,6 @@ cleanup_manager.register(ais_vessels)
 cleanup_manager.register(dsc_messages)
 cleanup_manager.register(deauth_alerts)
 
-# ============================================
-# WATERFALL SOURCE TRACKING
-# ============================================
-# Tracks whether waterfall data is being produced by a decoder's IQ pipeline
-# None = no active source, 'rtl_power' = standalone, 'pager'/'sensor' = decoder-driven
-waterfall_source: str | None = None
-
 # ============================================
 # SDR DEVICE REGISTRY
 # ============================================
@@ -666,7 +659,7 @@ def kill_all() -> Response:
     """Kill all decoder, WiFi, and Bluetooth processes."""
     global current_process, sensor_process, wifi_process, adsb_process, ais_process, acars_process
     global aprs_process, aprs_rtl_process, dsc_process, dsc_rtl_process, bt_process
-    global dmr_process, dmr_rtl_process, waterfall_source
+    global dmr_process, dmr_rtl_process
 
     # Import adsb and ais modules to reset their state
     from routes import adsb as adsb_module
@@ -675,7 +668,7 @@ def kill_all() -> Response:
 
     killed = []
     processes_to_kill = [
-        'rtl_fm', 'multimon-ng', 'rtl_433', 'rtl_sdr',
+        'rtl_fm', 'multimon-ng', 'rtl_433',
         'airodump-ng', 'aireplay-ng', 'airmon-ng',
         'dump1090', 'acarsdec', 'direwolf', 'AIS-catcher',
         'hcitool', 'bluetoothctl', 'dsd',
@@ -748,10 +741,9 @@ def kill_all() -> Response:
     except Exception:
         pass
 
-    # Clear SDR device registry and waterfall source
+    # Clear SDR device registry
     with sdr_device_registry_lock:
         sdr_device_registry.clear()
-    waterfall_source = None
 
     return jsonify({'status': 'killed', 'processes': killed})