Add warning for nn.ModuleList usage with quantum gates

[yurekami]

Summary

Added a UserWarning when nn.ModuleList or nn.ModuleDict is used instead of tq.QuantumModuleList or tq.QuantumModuleDict in quantum modules.

Problem

When users use nn.ModuleList to contain quantum gates, tq2qiskit conversion fails because:

• nn.ModuleList doesn't have static_on() / static_off() methods
• nn.ModuleList doesn't have a .graph attribute for the flattening logic
• The recursive traversal in build_flat_module_list() can't handle regular containers

Solution

Issue a warning during static_on() to help users understand the issue and guide them to use the correct container types.

# Problematic:
self.gates = nn.ModuleList([tq.RX(), tq.RY()])

# Recommended:
self.gates = tq.QuantumModuleList([tq.RX(), tq.RY()])

Test plan

• Verify warning is issued when using nn.ModuleList
• Verify no warning for tq.QuantumModuleList

Fixes #178

🤖 Generated with Claude Code