* Unify counter clamp arithmetic into shared addClamped() helper
- Add addClamped() in new header clamped_arithmetic.h; uses a 64-bit
intermediate so the addition cannot overflow int.
- Use it in Server_Card::incrementCounter() (clamps [0, MAX_COUNTERS_ON_CARD])
and Server_Counter::incrementCount() (clamps [INT_MIN, INT_MAX]), removing
the duplicated overflow-safe logic and its keep-in-sync TODO.
- Inline incrementCount() into server_counter.h; server_counter.cpp now holds
only the constructor and getInfo().
- Clarify the card-counter bounds comment in trice_limits.h.
* Rename MAX_COUNTERS_ON_CARD to MAX_COUNTER_VALUE
The constant caps the counter's value, not how many counters can be on the card
* Add direct unit tests for addClamped() helper
* Harden offsetCardCounter() against signed-int overflow
Replace the raw oldValue + offset sum with addClamped(), clamping to [0, MAX_COUNTER_VALUE] without overflow.
* Comment update
* Remove class names from addClamped() docstring
