implement performance optimizations

[isdaniel]

enhance sequence synchronization by using a temporary table for applied counts
implement performance optimizations for migration process & rel v.0.2.0

[codecov]

Codecov Report

❌ Patch coverage is 95.27559% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.96%. Comparing base (730da06) to head (03484cc).

Files with missing lines	Patch %	Lines
pg_dbmigrator/src/orchestrator.rs	0.00%	8 Missing ⚠️
pg_dbmigrator/src/sequences.rs	98.35%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main       #9      +/-   ##
==========================================
+ Coverage   89.49%   89.96%   +0.47%     
==========================================
  Files          16       16              
  Lines        5633     5850     +217     
==========================================
+ Hits         5041     5263     +222     
+ Misses        592      587       -5     

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[gemini-code-assist]

Code Review

This pull request bumps the version to 0.2.0 and introduces several performance optimizations, including parallel pre-flight checks using tokio::join! and batched sequence synchronization via PL/pgSQL to reduce network round-trips. It also refines table discovery to exclude internal and temporary schemas and improves integration test stability. Feedback suggests restricting the visibility of the sequence SQL builder to pub(crate) to prevent potential misuse of its internal logic regarding uninitialized sequences.