QEarn V2: fixed-term locks, 18% long-term cap and CCF surplus routing

[jtskxx]

This PR introduces QEarn V2 starting at epoch 227, with three fixed lock periods:

• 13 epochs: up to 3% total return
• 26 epochs: up to 6% total return
• 52 epochs: up to 18% total return

These are maximum returns for the full term, not APY. Actual returns depend on the available bonus and
participation

For each lock epoch:

• Up to 10% of the bonus funds the 13-epoch term
• Up to 20% funds the 26-epoch term
• At least 70%, plus unused short-term rewards and early-exit forfeitures, goes to the 52-epoch term
• Surplus above the 52-epoch 18% cap is transferred to CCF

Early exits

• Same-epoch unlocking is not allowed
• An early exit closes the complete position
• Only principal is returned; no reward is paid
• Partial early exits are not supported

Existing V1 positions keep their original rules

The V2 state is appended using PADDING at epoch 227, preserving the complete V1 state. Existing legacy interfaces
remain compatible and create 52-epoch positions after activation

Dedicated V2 procedures and queries are added for selecting and displaying the three terms

Coverage includes:

• V1/V2 coexistence
• All terms, caps, maturities and early exits
• Reward allocation and CCF transfers
• Legacy interface compatibility
• Randomized accounting tests
• QBond and QVault compatibility
• ABI and state-layout verification