Show amounts for OP_RETURN outputs

[Jacksper13]

Summary

• show the formatted output amount alongside every OP_RETURN message during transaction review
• preserve the existing OP_RETURN message rendering
• add simulator regression coverage for zero-value and nonzero-value OP_RETURN outputs

Root cause

render_output() calculated the output value before classifying the destination, but its OP_RETURN branch returned early without including that value in the trusted-display text.

Impact

Users can now review the full economic value of an OP_RETURN output before signing. This changes display formatting only; PSBT parsing, fee calculation, and signing behavior are unchanged.

Validation

• python -m py_compile for the changed Python files
• python -m pycodestyle for the changed Python files
• host execution of the OP_RETURN renderer regression script
• git diff --check
• GitHub Actions firmware, bootloader, simulator, tools, Python, Rust, and REUSE checks