feat: Add section_id field to conversation and message structures

[chyroc]

• Added last_section_id field to the conversation structure
• Added section_id field to the message structure
• Updated related documentation and tests to include section_id

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 98.13%. Comparing base (3b90ba4) to head (3e30806). Report is 1 commits behind head on main.

@@           Coverage Diff           @@
##             main     #103   +/-   ##
=======================================
  Coverage   98.12%   98.13%           
=======================================
  Files          41       41           
  Lines        3040     3050   +10     
=======================================
+ Hits         2983     2993   +10     
  Misses         57       57           

Files with missing lines	Coverage Δ
cozepy/chat/__init__.py	96.09% <100.00%> (+0.01%)	:arrow_up:
cozepy/conversations/__init__.py	100.00% <100.00%> (ø)
tests/test_conversation.py	100.00% <100.00%> (ø)