fix: make beacons session-only, slower and QSY-aware (#171)

Forgotten beacons kept filling the chat while nobody was at the station.

- The two enable switches are session state now: they start off, are
  never read from preferences.xml and are always stored as "false", so
  neither a stored switch nor an older release reading a newer file can
  start a beacon. The in-code default was "on" and started a beacon
  whenever the file was unreadable or had no <beaconCQ> block.
- The minimum interval rises from 1 to 5 minutes; the bundled template
  ships 10 instead of 1. Smaller stored values are raised when the
  timer is scheduled.
- BeaconFrequencyGuard switches a beacon off once a logger-reported
  transceiver frequency lies more than 2 kHz from the one reported when
  the beacon was switched on. UCXLog RadioInfo and Win-Test STATUS feed
  it wherever they already set MYQRG/SECONDQRG. Without SO2R the single
  radio stands for both categories, with SO2R each radio for its own.

Manual (DE/EN), changelog, website and PROJECT_CONTEXT updated.

Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NJ1tUJVmWChD9V5Pg7uH8X

github_docs/en-Contest-Workflow.md

@@ -95,7 +95,7 @@ During operation on a mainly fixed CQ frequency, `MYQRG` and `SECONDQRG` should
 
 The beacon can publish the current QRG, locator and antenna direction in the chat at regular intervals. Its variables are evaluated again for every transmission.
 
-Disable the beacon while scanning across several frequencies. An automatically published QRG is useful only while it is still correct.
+Disable the beacon while scanning across several frequencies. An automatically published QRG is useful only while it is still correct. When the logger supplies the frequency, KST4Contest switches the beacon off [by itself](en-Configuration#automatic-switch-off-after-a-frequency-change) once the radio has moved by more than 2 kHz. After every program start the beacon is off and has to be enabled again.
 
 Shortcuts and snippets should cover the messages required regularly, for example: