feat(settings): implement IDelegatedSettings for activity admin settings

[printminion-co]

Summary

Vanilla-clean extraction of the IONOS delegation patch carried in PR #2 (IONOS(admin-settings): convert to delegated setting, cherry-picked from ca3cd2e), prepared per upstream-to-vanilla-app.md for contribution to nextcloud/activity.

OCA\Activity\Settings\Admin changes from implements ISettings to implements IDelegatedSettings, adding getName() and getAuthorizedAppConfig(). This is app-side only — no ncw-config ADMIN_DELEGATION_MAP registration is included, so it stands on its own upstream.

Why

Every NC major re-applies this same one-file patch onto the fork (v31, now v32 in PR #2, v33 next). Upstreaming it retires that delta permanently. Sibling of the already-open nextcloud/bruteforcesettings#1246.

Preparation notes

• Branched directly off nextcloud/activity:master; this fork's master mirror is currently identical to it, so the diff is exactly the one commit.
• Commit message reworded to Conventional Commits. No IONOS(...) prefix, no NSW/HDNEXT token, no fork-internal PR or SHA reference.
• Original author and Signed-off-by: Kai Henseler preserved; no sign-off added.
• #[\Override] added to the two new methods — the v31-era source commit predates them, but upstream's Admin.php marks every other interface method with it, as does Create pr-feedback.yml nextcloud/activity#1246.

Verification

Run in the shared dev container (.dev/container/dev) from the ncw-server checkout:

• composer lint — clean
• composer cs:check — clean, 0 of 98 files need fixing
• composer psalm — could not run: the app pins Psalm 7.0.0-beta19, which requires PHP >= 8.3.16; the container has PHP 8.3.6. Pre-existing environment gap, identical for nc-password_policy, unrelated to this change.
• No test in the app touches the settings class.

Related

• Jira: NSW-808 (upstreaming), NSW-946 (the v32 fork work that surfaced it)
• Server PR consuming the fork line: IONOS(update): update IONOS-owned app submodules for Nextcloud v32 (NSW-946) ncw-server#324
• NC32 fork release carrying the patch meanwhile: IONOS(activity): NC32 fork release (NSW-946) #2
• Upstream PR: to follow, into nextcloud/activity:master