feat(rust): add full parser support and resolution for Rust codebases

[gopinathnelluri]

This PR adds full, comprehensive support for Rust codebases to code-review-graph. Previously, Rust call graphs were sparse and disconnected due to missing type associations, unparsed traits, and lack of path/scoped call resolution.
This implementation enables correct structural parsing of Rust features—including traits, inherent/trait impl blocks, relative/crate imports, and scoped calls—ensuring high-quality execution flow and impact radius analysis for Rust projects.

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Key Changes

1. AST Parsing & Extraction (code_review_graph/parser.py)

• Trait Nodes: Registered trait_item under Rust class types, allowing trait definitions to be parsed as Class nodes.
• impl Block Scope Association:
  • Inherent/trait impl blocks are now mapped to their target struct/enum scope (stripping generics) rather than the trait name.
  • Methods defined within impl blocks are qualified under the implementing struct (e.g., InMemoryRepo.save), matching how they are concrete-ly invoked.
• Inheritance Mapping (INHERITS Edges): Added Rust support to _get_bases to emit an INHERITS edge between the implementing struct and the trait in impl Trait for Struct blocks.
• Nested/Aliased Use Declarations: Implemented recursive flattening (_parse_rust_use_node) for complex Rust use statements (e.g. use a::{b, c::d}) and alias patterns (as).

2. Scoped Path & Module Resolvers (code_review_graph/parser.py)

• Module-to-File Resolution: Added Rust-specific path resolution to _do_resolve_module. It scans for Cargo.toml to identify the crate root, handles crate:: and self:: segments, resolves nested super:: references, and maps them to absolute .rs or mod.rs files.
• Scoped Method Call Resolution: Added _resolve_rust_scoped_call and integrated it in _resolve_call_target. It translates double-colon scoped calls (e.g. InMemoryRepo::new()) to dot-separated qualified method targets (e.g., InMemoryRepo.new), bridging the AST call-site to the graph method node.

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Verification & Testing

Automated Tests

Extended the test suite in tests/test_multilang.py with:

• Assertions for trait detection and INHERITS conformance tracking.
• Assertions for scoped call resolution (InMemoryRepo::new -> InMemoryRepo.new).
• Direct module path resolution tests under a mock Cargo structure verifying crate:: and super:: resolution.
  All 307 multilang tests pass successfully:

$ uv run pytest tests/test_multilang.py
collected 307 items
======================== 307 passed, 1 warning in 6.02s ========================