fix(click-buttons-across-tabs): Correct rate-limiter logic and settings parser
This commit addresses two issues:
First, the timestamp-based rate limiter was vulnerable to a
race condition. GM.setValue in Tab 1 did not propagate
before Tab 2 read the value, resulting in tabs submitting
in pairs and effectively doubling the submission rate.
This is fixed by removing the timestamp logic entirely and instead
awaiting a setTimeout for the requiredInterval after
submission, holding the navigator.lock for the duration.
Second, the settings menu for "submits per second" used parseInt,
which prevented entering fractional rates (e.g., 0.5 for a
2-second delay). This is changed to parseFloat, and the
alert text is updated.
