docs: bound the deletion window and cover the background overlay run

[enoch85]

Closes #155. Confirmed against a local clone of Maintainerr rather than the report summary.

What was added

Doc	Change	Upstream
docs/Rules.mdx	Media deleted after days is a whole number from 0 to 36500. The bound is enforced in the rule form, on PUT /api/collections, and on rule-group saves	c861c54f, #3549
docs/Overlays.md	Run Now and Reset All Overlays hand the work to the server and answer straight away, so a slow run cannot time out in the browser and closing the page does not stop it	c861c54f
docs/Overlays.md	Reset All Overlays also puts back an original Maintainerr saved but has no record of drawing on	c861c54f
docs/Overlays.md	Deleting a collection queues its overlay restore behind a run in progress instead of skipping it	#3558
docs/Overlays.md	A template is drawn onto the largest centered area of the artwork with the canvas shape, not stretched over the whole image	#3533
static/openapi-spec/maintainerr_api_specs.yaml	POST /api/overlays/process and DELETE /api/overlays/reset answer 202 now, not 201 and 200	c861c54f

Already covered by prior PRs

Drift item	Where
The countdown is drawn only when the action deletes, and the inheritance rules up to a show	#153
Overlays are reverted when a collection is deleted, and when it moves to an action that keeps files	#149, #153
Weblate translation flow, Display language, and the English fallback	#149

Skipped as not doc-worthy: #3550 and #3534 both restore behavior the docs already describe; the i18n, CI and tooling commits change no documented surface; and the three contracts files touch no DTO, so docs/API.md needs no edit beyond the two response codes above.

npm run format and npm run build both clean, no broken links.