Docs/Authorities: restructure maintenance.md as single source of truth (ILIAS-eLearning#11982)

Restructure docs/development/maintenance.md: components are listed
alphabetically by their folder name in components/ILIAS/, each with
a uniform authority block, and the file replaces the per-component
maintenance.json files as the single source of truth for
maintainership data.

Structural changes:
- one block per component folder with GitHub link and Feature-Wiki
  assignment ("Belongs to"); wiki-grouped folders (Login/Auth,
  ECS Interface, Study Programme, ...) share their authority data
- authority entries use the format
  [<github-username>](<link-to-docu-profile>), documented in
  "How Authority Assignments are Stored"
- "Tester" and "Unit-specific Guidelines, Rules, and Regulations"
  fields dropped (TB decisions, July 2026)
- all 164 maintenance.json files removed (163 component folders
  plus templates/maintenance.json)
- ilComponentBuildPluginInfoObjectiveTest::testScanDir no longer
  expects maintenance.json; dead maintenance.json links in
  components/ILIAS/Refinery/docs/CONTRIBUTING.md now point to the
  maintenance.md

Authority updates agreed with the maintainers (July/August 2026):
- AuthSOAP: Pascal Seeland removed -> mjansen, thojou
- OpenIdConnect: smeyer -> mjansen, thojou
- Cache, FileDelivery, FileServices -> fschmid
- soap -> minervis (githamo, sKarki999; De-Assign: TimoScheuer)
- VirusScanner -> unmaintained (rschenk stepped down)
- Html assigned to Security instead of Forum (component is the
  HTML-Purifier service)
- Init mapped to "Initialisation Service" (mjansen, tfuhrer,
  fschmid) instead of the Login/Auth group
- ILIASObject: username fixed fawinike -> skergomard (usr 44474)
- Feature-Wiki links added for BackgroundTasks, CmiXapi (xAPI),
  ContentPage, FileUpload (File), GlobalScreen, Group,
  IndividualAssessment, Taxonomy

Cleanup (TB decisions):
- Cloud and SystemFolder components removed; note: Cloud contained
  the RemoveCloudDBUpdate setup migration
- Http_, UI_ and BackgroundTasks_ intentionally stay listed as
  unmaintained

For the Technical Board of the ILIAS Association

Author: marvimarv