fix: escape quotes in DOT renderer (#212)

Lines 152-153 used unescaped double quotes inside
Python double-quoted string literals. Switched to
single-quoted strings.

scripts/dependency_graph.py

@@ -149,8 +149,8 @@ def to_dot(graph: dict) -> str:
     """Generate DOT format output."""
     lines = ["digraph dependencies {"]
     lines.append("  rankdir=LR;")
-    lines.append("  node [shape=box, style=filled, fillcolor="#1a1a2e", fontcolor="#e6edf3"];")
-    lines.append("  edge [color="#4a4a6a"];")
+    lines.append('  node [shape=box, style=filled, fillcolor="#1a1a2e", fontcolor="#e6edf3"];')
+    lines.append('  edge [color="#4a4a6a"];')
     lines.append("")
 
     for repo, data in sorted(graph.items()):