fix(position): halve the stationary/fixed-position broadcast floor to 6h (#11606)

The 12h floor introduced with traffic management was too aggressive: a
fixed_position or stationary node goes quiet for half a day after its
boot broadcast, so anything that missed that one packet - a node that
joined later, or one that restarted - shows it with no position until
the next refresh.

Drop the floor to 6h, and drop the traffic-management identical-position
dedup window from 11h to 5h with it. The two are a pair: the dedup window
was deliberately sized just under the broadcast floor so a stationary
node's periodic refresh clears its neighbours' window instead of being
dropped as a duplicate. Leaving it at 11h would have made the extra
broadcast pure airtime - aired, then discarded by every receiver - so the
mesh would still have seen a 12h refresh.

Role caps are unchanged and still bind: tracker 1h, lost-and-found 15m.
Both remain shorter than the new 5h default, so those exceptions apply
exactly as before.

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

src/modules/PositionModule.cpp

@@ -558,7 +558,7 @@ int32_t PositionModule::runOnce()
 
     bool waitingForFreshPosition = (lastGpsSend == 0) && !config.position.fixed_position && !nodeDB->hasLocalPositionSinceBoot();
 
-    // Hold to the 12h floor when fixed_position (every role: pinning yourself forfeits the
+    // Hold to the 6h floor when fixed_position (every role: pinning yourself forfeits the
     // exception) or when stationary. A real move still goes out early via smart-broadcast below.
     // Not-fixed exceptions: lost-and-found broadcasts freely; trackers judge movement at their
     // own (unclamped) precision rather than the on-wire one (useConfiguredPrecision).