refactor: move scattered business logic into domain

- CodeGraph::merge_project_edges() replaces presentation-layer function
- Language::is_test_file() centralises test file detection (was in walkdir)
- AnalysisConfig::is_standard_excluded() centralises default dir exclusions (was in walkdir)
- normalize_cargo_package() / normalize_python_package() in domain replace duplicated normalisers in each adapter
- walkdir, cargo-workspace, python-project updated to call domain methods

crates/adapters/python-project/src/python_project_analyzer.rs

@@ -5,7 +5,7 @@ use serde::Deserialize;
 
 use archlens_domain::{
     CodeElement, CodeElementKind, CodeGraph, DomainError, FilePath, Relationship, RelationshipKind,
-    ports::ProjectAnalyzer,
+    normalize_python_package, ports::ProjectAnalyzer,
 };
 
 pub struct PythonProjectAnalyzer;
@@ -59,7 +59,7 @@ fn extract_dep_name(dep: &str) -> &str {
 }
 
 fn normalize(name: &str) -> String {
-    name.to_lowercase().replace(['-', '.'], "_")
+    normalize_python_package(name)
 }
 
 impl ProjectAnalyzer for PythonProjectAnalyzer {