Fixes across On-Call, Uptime and Retro

A round of reliability fixes shipped with this release.

Acknowledging or resolving an alert twice, for example with a double click, no longer causes an error.
When two people take over the same alert at the same moment, the timeline matches who ends up holding it.
Acknowledging an alert again after an acknowledgement timeout keeps the escalation on hold.
Identical alerts that arrive at the same moment are reliably merged into one.
Phone numbers are stored and dialled in international format, and a verification call verifies the number it actually called.
Editing the title of a published incident keeps its public impact.
Blank and overly long names are refused with a clear message.
The alert date filter uses your local day, and the filter panel opens over the page instead of pushing it down.
Links to alerts or incidents that no longer exist show a "not found" page.

Retro live updates reconnect on their own after your session refreshes.
Pressing Create twice creates one retro, and creating an organization from the switcher creates exactly one.