Add a "Check filesystem" action to the Services pill:
- SERVICES_FS_MAP: the feature -> FID list transcribed from
docs/services-editor.md §A (127 file-backed + 34 capability features,
157 distinct FIDs; a completeness/data test pins it).
- servicesFsReport: pure two-direction check - declared features whose
mapped files are absent, and present files whose features are
undeclared. FID-level (not DF-exact) for this first pass; documented.
- The Check runs the tree probe (once per session) and renders the
missing/extra lists or the "matches" line, with an FID-level note.
Also fix a doc typo (eCall Data's EF.FDN was written as 6F3A = EF.ADN).
Frontend 1120 + Python 1090 tests green. (Version/sw bump still
deferred for the decoded-editing batch.)