fix: make JsonSerializable type alias read-only

[Pijukatel]

Bumping ty to 0.0.83 fails type-check (32 errors): it rejects e.g. list[dict[str, int]] as JsonSerializable because list/dict are invariant.
Fix: JsonSerializable uses read-only Mapping/Sequence, so callers can keep passing plain dicts and lists. The alias is only used for inputs that get serialized.
The lock bumps only ty to 0.0.83 so CI proves the fix; unit tests pass; also clears the push_items error in apify-sdk-python.

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https://claude.ai/code/session_018m46SvjMFWEVxC4RDuegPN

[codecov]

Codecov Report

❌ Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 95.24%. Comparing base (77a3475) to head (c8126d2).

Files with missing lines	Patch %	Lines
src/apify_client/types.py	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1072      +/-   ##
==========================================
- Coverage   95.25%   95.24%   -0.02%     
==========================================
  Files          59       59              
  Lines        5547     5548       +1     
==========================================
  Hits         5284     5284              
- Misses        263      264       +1     

Flag	Coverage Δ
integration	92.05% <0.00%> (+0.19%)	⬆️
unit	87.40% <0.00%> (-0.02%)	⬇️

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