feat(poller): authorize funder CowShed

[igorroncevic]

Summary

Gasless JIT TWAP setup and cancellation can now register or revoke a Poller schedule through the funder’s official CowShed. The funder EOA remains authorized, while unrelated EOAs and CowSheds are rejected.

The Poller derives the CowShed from an immutable factory instead of trusting a caller-supplied address. Schedule IDs, events, funding history, and permissionless polling are unchanged.

Related: #125

Validation

• 27 Poller tests pass, including official, fake, and cross-user CowShed cases.
• Changed-file formatting and git diff --check pass.
• Full suite: 101 pass; one unrelated TWAP fuzz seed fails with MemoryOOG identically on this branch and its feat: pollFunds for just-in-time order funding #125 base.
• Five independent review lenses reported no defects.

Post-Deploy Monitoring & Validation

• Verify the deployed COW_SHED_FACTORY and COMPOSABLE_COW immutable values before use.
• During the first Gnosis proof, confirm the factory-derived CowShed can register and revoke while fake CowSheds revert with UnauthorizedCaller.
• Treat a factory/address mismatch or unexpected authorization failure as a stop condition; do not use that deployment and redeploy with the reviewed constructor values.
• Validation window and owner: first end-to-end Gnosis proof, owned by the PR author.

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