fix(cargo,dart): handle multi-byte chars and wildcard version matching

Cargo parser: adjust search_start to char boundary when slicing
content for dependency name lookup, preventing panic on files
containing multi-byte UTF-8 characters.

Dart version: treat "*" as wildcard (alias for "any") to match
the convention used by deps-lsp core when fetching latest versions.

Author: bug-ops

crates/deps-dart/src/version.rs

@@ -32,7 +32,7 @@ pub fn compare_versions(a: &str, b: &str) -> Ordering {
 pub fn version_matches_constraint(version: &str, constraint: &str) -> bool {
     let constraint = constraint.trim();
 
-    if constraint.is_empty() || constraint == "any" {
+    if constraint.is_empty() || constraint == "any" || constraint == "*" {
         return true;
     }