Refactor firmware for clarity; no functional changes

- main.c: file-header comment describing the hardware and operation, logic
  split into named phases (sleep_until_interrupt, wake_peripheral_rails,
  take_counts_snapshot, send_wheel_counts_report, handle_minute_alarm,
  init_all_hardware); shared state renamed to say what it is and made static.
- rfm69.c: reorganized into six labeled sections; cond_1/2/3 and hash scratch
  globals replaced by a reply_acknowledges() helper with clear locals; packet
  layout and every init register write documented.
- LOG() macro (compiled out when DO_UART is off) replaces the #if DO_UART
  blocks that obscured the logic.
- Drivers: file-header comments; named RTC_REG_*/RTC_ALM_MASK_BIT constants;
  EEPROM spool scheme documented; ADC_CHANNEL_BANDGAP named; repeated pin
  if/else helpers collapsed to SET_PIN_TO().
- Removed unused globals/buffers and commented-out code; ran clang-format
  with the project style.

Register writes and radio protocol are byte-identical. Builds clean under
-Wall -Wextra on gnu17 and c23; flash 13028 -> 12830 B, static RAM
1038 -> 999 B.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YVJKatfeMJjAmuH9KYiLuv

avr_code/interrupts.c

@@ -1,7 +1,8 @@
 
 #include "interrupts.h"
 
-void init_pins(void) {
+void init_pins(void)
+{
 
     // The reed switch (PD3/INT1) switches to ground and the RTC alarm output
     // (PD2/INT0) is open-drain, so both need the internal pull-up. Leaving them
@@ -19,27 +20,32 @@ void init_pins(void) {
 // asynchronous. Each handler masks its own interrupt while the source is still
 // asserted, so the low level does not retrigger in a loop.
 
-void set_up_reed_interrupt(void) {
+void set_up_reed_interrupt(void)
+{
     EICRA &= ~((1 << ISC11) | (1 << ISC10));
     EIMSK |= (1 << INT1);
 }
 
-void set_up_minute_interrupt(void) {
+void set_up_minute_interrupt(void)
+{
     EICRA &= ~((1 << ISC01) | (1 << ISC00));
     EIMSK |= (1 << INT0);
 }
 
-void reed_interrupt_enable(void) {
+void reed_interrupt_enable(void)
+{
     EIFR = (1 << INTF1); // Drop anything latched while we were masked
     EIMSK |= (1 << INT1);
 }
 
-void minute_interrupt_enable(void) {
+void minute_interrupt_enable(void)
+{
     EIFR = (1 << INTF0);
     EIMSK |= (1 << INT0);
 }
 
-void wdt_isr_enable(void) {
+void wdt_isr_enable(void)
+{
     uint8_t sreg = SREG;
     cli();
     wdt_reset();
@@ -57,7 +63,8 @@ void wdt_isr_enable(void) {
     SREG = sreg; // Restore, never blanket-sei(): these run inside an ISR
 }
 
-void wdt_isr_disable(void) {
+void wdt_isr_disable(void)
+{
     uint8_t sreg = SREG;
     cli();
     wdt_reset();