UI: Fix text stacking in paused indicator

Currently, the paused indicator is never undone, instead relying on the
update timer to eventually erase it away when the recording duration is
updated. If the user spams pause fast enough, the indicator will stack
several times before it is erased - especially if the unpaused branch in
the update timer never has a chance to run.

Instead of mutating the recordTime text on pause and requiring an undo,
extract the UI update to a separate function which computes the full
text based on the current state. Call this function when pause is
toggled, thereby forcing an accurate UI update that either does or does
not incude the paused text.

An added benefit is that the paused indicator now disappears
immediately.
This commit is contained in:
Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f