Add FPV DETECT external app with Auto-scan FPV Presence Receiver (#3084)

* fpv_rx external app implemented

* FPV DETECT: PR feedback and Copilot suggestions

- Rename app from 'FPV RX' to 'FPV DETECT' (menu and title)
- Add fpv_rx to EXTAPPLIST in external.cmake so app is included in build
- Set external_apps_address_end = 0xAE010000 in external_app_info.py
- Fix clang-format in ui_fpv_rx.cpp (update_visual_state block)
- Re-sample adjacent channels during candidate verification so
  neighbor_margin lock decision uses current measurements instead of
  stale channel_memory_ from scan (reduces false/missed locks)

Made-with: Cursor

* Rename fpv_rx to fpv_detect (files, dir, app id)

- Rename directory external/fpv_rx -> external/fpv_detect
- Rename ui_fpv_rx.{cpp,hpp} -> ui_fpv_detect.{cpp,hpp}
- Update external.cmake and external.ld for fpv_detect
- Namespace fpv_rx -> fpv_detect, class FpvRxView -> FpvDetectView
- Section/symbol .app_fpv_rx -> .app_fpv_detect

Made-with: Cursor

firmware/application/external/external.ld

@@ -103,7 +103,7 @@ MEMORY
     ram_external_app_same_tx   (rwx) : org = 0xADFE0000, len = 32k
     ram_external_app_kiss_tnc  (rwx) : org = 0xADFF0000, len = 32k
     ram_external_app_epirb_tx  (rwx) : org = 0xAE000000, len = 32k
-
+    ram_external_app_fpv_detect (rwx) : org = 0xAE010000, len = 32k
 }
 
 SECTIONS
@@ -588,5 +588,11 @@ SECTIONS
         KEEP(*(.external_app.app_epirb_tx.application_information));
         *(*ui*external_app*epirb_tx*);
     } > ram_external_app_epirb_tx
+
+    .external_app_fpv_detect : ALIGN(4) SUBALIGN(4)
+    {
+        KEEP(*(.external_app.app_fpv_detect.application_information));
+        *(*ui*external_app*fpv_detect*);
+    } > ram_external_app_fpv_detect
 }