Rename Base to Model and update tests and type hints

[TaiSakuma]

No description provided.

[codecov]

Codecov Report

Attention: 9 lines in your changes are missing coverage. Please review.

Comparison is base (35b2648) 92.47% compared to head (eff0d8c) 94.31%.
Report is 101 commits behind head on main.

Files	Patch %	Lines
tests/alembic/conftest.py	78.94%	4 Missing ⚠️
tests/db.py	94.73%	2 Missing ⚠️
src/nextline_rdb/utils/safe.py	95.45%	1 Missing ⚠️
src/nextline_rdb/utils/strategies/misc.py	96.77%	1 Missing ⚠️
tests/test_write.py	96.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main       #8      +/-   ##
==========================================
+ Coverage   92.47%   94.31%   +1.84%     
==========================================
  Files          51       70      +19     
  Lines        1395     1988     +593     
  Branches      243      375     +132     
==========================================
+ Hits         1290     1875     +585     
- Misses         83       91       +8     
  Partials       22       22              

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