Issue 2: Optimize imports for type checking with TC rules

[ParticularlyPythonicBS]

Enable and fix all TC (flake8-type-checking) rules to move type-only imports into TYPE_CHECKING blocks, reducing runtime import overhead and improving startup performance.

Scope TC001: Move application imports into TYPE_CHECKING blocks TC003: Move standard library imports into TYPE_CHECKING blocks TC004: Fix imports incorrectly placed in TYPE_CHECKING (used at runtime)