fix(mobile-call): spurious "did not answer" state at call start and after the callee accepts

[Adamskiee]

Reported during QA session.

What happened

The caller's call room shows the "did not answer" / no-answer terminal state at two moments where it makes no sense:

1. Immediately at the start of a call, before the callee has had any chance to answer.
2. Again after the callee has already accepted the call.

What I expected

The no-answer state should only appear when the callee genuinely fails to answer within the ringing timeout, and it should never appear once the callee has accepted.

Steps to reproduce

1. On device A, start a call to device B.
2. Watch device A's call room in the first couple of seconds — the no-answer state flashes up.
3. On device B, accept the call.
4. Watch device A's call room again — it shows the no-answer state even though B accepted.

Additional context

The call room has a ringing timeout that drives the no-answer state, and it also reacts to remote call-ended signals carrying a "missed" status. Either a stale/mistimed missed signal from a previous call attempt is being applied to the current one, or the ringing timeout is not being cancelled when the callee accepts.

Likely related to the terminal-state handling in the mid-call "Call ended" issue and to stale per-call state on repeated calls.

[Adamskiee]

May share a cause with the stale per-call state cluster (#292, #298, #304) — stale signals from a previous call attempt being applied to the current session.