cpf/enhancement: Implement import extraction with tree-sitter

[shivasurya]

This PR implements comprehensive import extraction for Python code using tree-sitter AST parsing. It handles all three main import styles:

1. Simple imports: import module
2. From imports: from module import name
3. Aliased imports: import module as alias and from module import name as alias

The implementation uses direct AST traversal instead of tree-sitter queries for better compatibility and control. It properly handles:

• Multiple imports per line (from json import dumps, loads)
• Nested module paths (import xml.etree.ElementTree)
• Whitespace variations
• Invalid/malformed syntax (fault-tolerant parsing)

Key functions:

• ExtractImports(): Main entry point that parses code and builds ImportMap
• traverseForImports(): Recursively traverses AST to find import statements
• processImportStatement(): Handles simple and aliased imports
• processImportFromStatement(): Handles from-import statements with proper module name skipping to avoid duplicate entries

Test coverage: 92.8% overall, 90-95% for import extraction functions

Test fixtures include:

• simple_imports.py: Basic import statements
• from_imports.py: From import statements with multiple names
• aliased_imports.py: Aliased imports (both simple and from)
• mixed_imports.py: Mixed import styles

All tests passing, linting clean, builds successfully.

This is Pass 2 Part A of the 3-pass call graph algorithm.

Checklist:

• Tests passing (gradle testGo)?
• Lint passing (golangci-lint run this requires golangci-lint)?

[safedep]

SafeDep Report Summary

No dependency changes detected. Nothing to scan.

_{This report is generated by SafeDep Github App}

[codecov]

Codecov Report

❌ Patch coverage is 86.66667% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 73.94%. Comparing base (4e21322) to head (1e53414).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
sourcecode-parser/graph/callgraph/imports.go	86.66%	4 Missing and 4 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #324      +/-   ##
==========================================
+ Coverage   73.65%   73.94%   +0.29%     
==========================================
  Files          25       26       +1     
  Lines        2615     2675      +60     
==========================================
+ Hits         1926     1978      +52     
- Misses        643      647       +4     
- Partials       46       50       +4     

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