Reorganize code in prep for hardware decoupling and port to C++

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/avclan/statustimer.h

@@ -0,0 +1,38 @@
+/*
+                        AVCLAN-Mockingboard
+    Copyright (C) 2015 Allen Hill <allenofthehills@gmail.com>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+// ~1 Hz status-update tick, driven by the RTC overflow. The overflow handler
+// (ISR(RTC_CNT_vect)) lives in the app (sniffer.c); this module owns only the
+// RTC hardware configuration and enable/disable/reset of the tick.
+
+#ifndef STATUSTIMER_H
+#define STATUSTIMER_H
+
+// One-time RTC hardware bring-up (clock source + period). Leaves the overflow
+// interrupt disabled.
+void statustimer_init();
+
+// Reset the count so the next tick is ~1 s out, and enable the overflow tick.
+void statustimer_reset();
+
+// Enable / disable the ~1 Hz overflow interrupt (bare register RMW; wrap in a
+// critical section if called with interrupts enabled and concurrency matters).
+void statustimer_enable();
+void statustimer_disable();
+
+#endif // STATUSTIMER_H