CAN-003 | Add DBC to C codegen pipeline

[wxkim]

Problem statement: what's wrong with it?

• CAN boilerplate is manual and easy to drift.

Ideal situation: describe the solution you'd like.

• One command to generate C pack/unpack files from DBC.

Proposed solutions: describe alternatives you've considered

• Manual C updates.
• DBC-driven codegen (preferred).

Additional context

• Renumbered from prior 008 item.