✨ feat: Resolve relative imports to absolute module names

[heumsi]

Summary

• Resolve relative imports (e.g., from . import foo, from ..module import bar) to absolute module names in the parser
• Previously, relative imports were silently skipped during analysis, meaning dependency violations via relative imports went undetected
• Over-level relative imports (exceeding project root) are silently skipped

Closes #7

Test plan

• from .sibling import x (level 1, with module) resolves correctly
• from . import x (level 1, no module) resolves correctly
• from ..other import y (level 2, with module) resolves correctly
• Over-level relative import is silently skipped
• Relative import from __init__.py resolves correctly
• Existing tests still pass (40/40)

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