[Contract] Implement Detokenization Proposal and Execution Flow

[yusuftomilola]

Mechanism for unwinding fractional ownership by proposing and executing detokenization through a governance vote.

Requirements

propose_detokenization(env, asset_id, proposer):

• Proposer must authenticate and hold tokens
• Creates a DetokenizationProposal with a unique proposal ID
• Creates a voting proposal (links to the Voting module)
• Returns the proposal ID

execute_detokenization(env, asset_id, proposal_id):

• Checks that the linked voting proposal has passed
• Burns all outstanding tokens
• Resets the tokenized asset record
• Emits a detokenized event

get_detokenization_proposal(env, asset_id) — Returns current proposal or error

is_detokenization_active(env, asset_id) — Bool check

Acceptance Criteria

• Execution fails if vote has not passed
• All tokens burned after successful execution
• Cannot propose detokenization twice simultaneously