Adds a discreet "Ver historial" text-button under the existing version
chip in `/settings` › About. The button toggles a local `showChangelog`
$state that drives the ChangelogModal mounted at the bottom of the
template, after every other modal so it stacks correctly.
Playwright CL-01 verifies the trigger → modal → CHANGELOG header path,
CL-02 verifies Escape closes the modal. Both pass against the bundled
?raw import (no fetch, exercises the production load path).
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
