Display voting power at the time of proposal creation

[denviljclarke]

📝 Description

The governance UI shows users their total voting power based on their locked balance. However, this value must reflect the historical voting power when each proposal was created since voting power can change if users lock tokens after a proposal is made. This issue was highlighted when Markus noticed his voting power was 0% because he had locked his tokens after the proposal was created. We need to modify the UI to display the correct historical voting power specific to each proposal's creation timestamp to fix this.

✅ Acceptance Criteria

• Display the historical voting power from the time of proposal creation instead of the current voting power
• Add clear UI indication that voting power is calculated from proposal creation time
• Add tests covering different voting power scenarios (tokens locked before/after proposal creation)