chore(deprecations): scope literal lookup to function bodies

[lackas]

Resolves the 5 long-standing "deprecated features used in code" warnings that the deprecation checker has been reporting on every master push since #707. The Format workflow's validate deprecation database step has been red continuously since the deprecation DB was introduced — but the warnings turn out to all be false positives from the segment-lookup heuristic.

The flagged features

  ventilation.operating.programs.comfort        Used in: PyViCareVentilationDevice.py
  ventilation.operating.programs.eco            Used in: PyViCareVentilationDevice.py
  ventilation.operating.programs.forcedLevelFour  Used in: PyViCareVentilationDevice.py
  ventilation.operating.programs.holiday        Used in: PyViCareVentilationDevice.py
  ventilation.operating.programs.silent         Used in: PyViCareVentilationDevice.py

Why these aren't actually used

PyViCareVentilationDevice.py has exactly one getProperty call against ventilation.operating.programs.*, in getVentilationPrograms():

for program in ['basic', 'intensive', 'reduced', 'standard', 'standby', 'holidayAtHome', 'permanent']:
    if self.getProperty(f"ventilation.operating.programs.{program}") is not None:
        ...

Zero overlap with the flagged features. But the same file has, in the orthogonal getVentilationQuickmodes(), a separate loop that queries the unrelated ventilation.quickmodes.* path:

for quickmode in ['comfort', 'eco', 'forcedLevelFour', 'holiday', 'standby', 'silent']:
    if self.getProperty(f"ventilation.quickmodes.{quickmode}") is not None:

The checker's confirmation step searches for each candidate segment value ('comfort', …) as a string literal anywhere in the same file — so it found them in the quickmodes loop and accepted them as proof that ventilation.operating.programs.comfort is referenced. Same mechanism for the other four.

The fix

find_code_usage() now uses ast.parse to extract each FunctionDef / AsyncFunctionDef body as an independent scope. feature_matches_code() searches only within the scope that contains the getProperty call. Top-level / class-body statements outside any function are scanned as one residual scope so non-function code isn't missed.

Verification

• python check_deprecations.py --update now exits 0 against master (was 1)
• The 5 spurious in-code warnings are gone; the 107 past-removal features with no real use now correctly classify under "Past removal date (not used in code)"
• Confirmed no real positives are silently swept: there's exactly one ventilation.operating.programs.* getProperty call in the whole codebase (the one in getVentilationPrograms), and none of its iteration values are in the DB
• All 729 PyViCare tests still pass