Add FoundationFunder contract

[nourharidy]

A Solidity smart contract for rate-limited ERC20 token disbursement. A governance address (gov) sets per-token quarterly budgets that stream linearly over time. A beneficiary can pull tokens up to the accrued budget, and optionally authorize delegates with their own independent streaming sub-limits.

How It Works

Roles

• Gov — Sets quarterly token budgets and can transfer its own role or the beneficiary role.
• Beneficiary — Pulls tokens from gov's balance within the quarterly budget. Can authorize delegates and transfer its own role.
• Delegates — Pull tokens on behalf of the beneficiary, subject to both the quarterly budget and their own per-delegate streaming limit.

Streaming Token Buckets

Budgets are not unlocked all at once. They accrue linearly over time using a token bucket model:

• Quarterly bucket — Gov sets a quarterlyLimit per token. The available balance streams from 0 to quarterlyLimit over 90 days. After a pull, the bucket continues accruing from its reduced level. The available balance is capped at quarterlyLimit (no accumulation beyond one quarter).

• Delegate bucket — The beneficiary configures each delegate with a limitAmount and interval. The delegate's available balance streams from 0 to limitAmount over interval seconds, functioning identically to the quarterly bucket but on a custom timescale.

When a delegate pulls tokens, both buckets are checked and consumed. The pull succeeds only if the requested amount is within both the quarterly budget and the delegate's own limit.

Pull Mechanism

Tokens are transferred directly from gov's wallet via transferFrom — the contract never holds funds. Gov must approve the contract to spend its tokens.

Every pull requires a reason string that is emitted in the FundsPulled event for transparency and auditability.

Mid-Stream Configuration Changes

Quarterly limits and delegate configs can be updated at any time. When changed, the contract first accrues any tokens earned under the old parameters, then applies the new config. If the new limit is lower than the current accrued balance, the balance is capped to the new limit.