[codex] Stabilize Harbor-backed test runs

[quinnj]

Summary

• switch the MySQL.jl test suite to manage its own temporary MySQL container via Harbor.jl
• simplify local and CI setup so tests only assume Docker is available
• restore a stable Connector/C SSL verification default and fix option/result cleanup paths surfaced by current Connector/C and MySQL behavior
• close load-time prepared statements so bulk loads do not poison later queries on the same connection
• raise the minimum supported Julia version to 1.10, the current Julia LTS line as of April 23, 2026

Validation

• julia --project=. -e 'using Pkg; Pkg.test(; coverage=false)'

[codecov]

Codecov Report

❌ Patch coverage is 83.33333% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.82%. Comparing base (bfdcb57) to head (8b03250).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/api/capi.jl	66.66%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #235      +/-   ##
==========================================
+ Coverage   63.40%   69.82%   +6.41%     
==========================================
  Files          10       10              
  Lines        1115     1183      +68     
==========================================
+ Hits          707      826     +119     
+ Misses        408      357      -51     

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