Task 1: DAO Governance for Milestone Approvals
- Add propose_milestone_approval() function for admins to initiate voting
- Add vote_milestone() function restricted to council members
- Automatic token transfer when voting threshold is reached
- Track votes with voting deadlines and prevent double voting

Task 2: Cliff Period for Grant Streams
- Add cliff_end timestamp to Grant struct
- Update withdraw() to return 0 if current_time < cliff_end
- Include cliff time in accrued calculations once passed

Task 3: Team-Based Grant Distribution
- Replace single grantee with grantees: Map<Address, u32> (basis points)
- Update withdraw() to accept caller address and calculate specific shares
- Assert total shares equal 10,000 basis points (100%) during creation
- Track individual withdrawals per team member

Additional Features:
- Enhanced error handling for governance operations
- Support for multi-sig threshold voting (e.g., 3-of-5)
- Per-team member withdrawal tracking
- Comprehensive access control for council members