fix: resolve ZeroDivisionError false positives via AST-based detection

[Prakhar54-byte]

Description
This PR resolves the false positive ZeroDivisionError reports by replacing the broad regex-based detection with a high-precision
AST-based analyzer. This significantly reduces noise in the analysis results and adds the capability to track zero-division
risks through function parameters.

Key Changes:

• Engine Migration: Removed the noisy ZeroDivisionError regex from the rule-based engine that was flagging valid code like x /
  2.
• AST Detection: Implemented direct literal zero-division detection (e.g., x / 0) using Python's Abstract Syntax Tree.
• Deep Tracking: Added detection for literal 0 passed as an argument to function parameters that are subsequently used as
  divisors.
• UX Enhancement: Updated the ast_analyzer to include line-numbered code context for all detections.
• Testing: Added comprehensive regression tests in tests/test_ast_analyzer.py.

Related Issue
Fixes #338

Type of change

• Bug fix
• New feature / enhancement
• Documentation update
• Test addition
• Refactor

Checklist

• x] I have read [CONTRIBUTING.md (../CONTRIBUTING.md)
• My branch is up to date with main
• I have run pytest -v and all tests pass
• I have not introduced duplicate issues or features
• My PR title follows the format: fix: resolve ZeroDivisionError false positives via AST-based detection
• I have added tests for new features
• No hardcoded secrets or API keys in my code
• This PR is linked to a GSSoC 2026 issue

Test evidence

1 $ cd backend && pytest tests/test_ast_analyzer.py -v
2 ============================= test session starts ==============================
3 platform linux -- Python 3.11.15, pytest-9.0.3, pluggy-1.6.0
4 rootdir: /home/prakhar/Downloads/AI-dev-assistant/backend
5 plugins: anyio-4.13.0, asyncio-1.3.0
6 collected 13 items                                                              
7
8 tests/test_ast_analyzer.py::test_unreachable_code PASSED                 [  7%]
9 tests/test_ast_analyzer.py::test_unused_import PASSED                    [ 15%]

10 tests/test_ast_analyzer.py::test_unused_argument PASSED [ 23%]
11 tests/test_ast_analyzer.py::test_clean_code_no_false_positives PASSED [ 30%]
12 tests/test_ast_analyzer.py::test_correct_line_number_unreachable PASSED [ 38%]
13 tests/test_ast_analyzer.py::test_self_not_flagged_as_unused PASSED [ 46%]
14 tests/test_ast_analyzer.py::test_underscore_param_not_flagged PASSED [ 53%]
15 tests/test_ast_analyzer.py::test_used_alias_not_flagged PASSED [ 61%]
16 tests/test_ast_analyzer.py::test_too_many_returns_exact_boundary PASSED [ 69%]
17 tests/test_ast_analyzer.py::test_unreachable_only_flags_after_not_before PASSED [ 76%]
18 tests/test_ast_analyzer.py::test_nested_function_returns_not_counted_in_outer PASSED [ 84%]
19 tests/test_ast_analyzer.py::test_deep_nesting_exact_boundary PASSED [ 92%]
20 tests/test_ast_analyzer.py::test_zero_division PASSED [100%]
21
22 ============================== 13 passed in 0.03s ==============================

[imDarshanGK]

@Prakhar54-byte update your branch with the latest main changes

[Prakhar54-byte]

Hi @imDarshanGK, I've updated the branch with the latest main changes and all checks are passing cleanly. Since the
repository is highly active and conflicts happen frequently, could you please review and merge this when you get a chance
so
it doesn't fall out of date again? Thank you!

[imDarshanGK]

@Prakhar54-byte CI failing

[Prakhar54-byte]

@imDarshanGK ci failing resolved pls check

[Prakhar54-byte]

Hi @imDarshanGK, I've updated the branch with the latest main changes and all checks are passing cleanly. Since the
repository is highly active and conflicts happen frequently, could you please review and merge this when you get a chance
so
it doesn't fall out of date again? Thank you!

[imDarshanGK]

@Prakhar54-byte update the branch with the latest main changes