Add recursion guard to traceSymbol in Java and Python detection engines

[Ayush-Patel-56]

Summary

traceSymbol in both JavaDetectionEngine and PythonDetectionEngine follows variable initializer chains recursively but has no cycle detection. A self-referential or mutually recursive assignment (e.g. x = x) would cause a StackOverflowError at analysis time.

Steps to reproduce

// hypothetical pathological input
SomeType x = x; // self-referential

Expected behavior

Detection gracefully stops at the cycle and returns the last seen symbol.

Suggested fix

Track visited symbols in a Set and return early if a symbol has already been seen during the current trace.

private Symbol traceSymbol(Symbol symbol, Set<Symbol> visited) {
    if (!visited.add(symbol)) return symbol;
    // ... existing logic
}

Context

Identified during review of PR #390. The fix for intermediary variable detection intentionally left this out to keep the scope minimal. Tracked here as a follow-up.