feat: add announcePlannedUpgrade flow for ServiceProviderRegistry

[Chaitu-Tatipamula]

Summary

This PR covers the ServiceProviderRegistry side of FS #355 by adopting the announcePlannedUpgrade pattern already used by FilecoinWarmStorageService. PDPVerifier changes are implemented in a separate PR in pdp and are not included here.

Changes

ServiceProviderRegistry contract

• Add PlannedUpgrade struct and nextUpgrade storage field
• Add UpgradeAnnounced(PlannedUpgrade) event
• Implement:
  • announcePlannedUpgrade(PlannedUpgrade plannedUpgrade) — owner-only, validates code size and afterEpoch > block.number, stores the plan and emits UpgradeAnnounced
  • getNextUpgrade() returns (address nextImplementation, uint96 afterEpoch) — exposes the planned upgrade via the proxy
• Update _authorizeUpgrade(address newImplementation) to:
  • Require newImplementation == nextUpgrade.nextImplementation
  • Require block.number >= nextUpgrade.afterEpoch
  • Clear the stored plan on successful upgrade
• Update migrate(string newVersion) to:
  • public onlyProxy onlyOwner reinitializer(2)
  • Emit ContractUpgraded(newVersion, ERC1967Utils.getImplementation())

Upgrade scripts

• Add tools/announce-planned-upgrade-registry.sh
  • Announces a planned upgrade for a ServiceProviderRegistry proxy using announcePlannedUpgrade((address,uint96))
• Add tools/upgrade-registry.sh
  • Reads getNextUpgrade() from the registry proxy
  • Verifies the planned implementation and afterEpoch
  • Calls upgradeToAndCall(address,bytes) with migrate(string) and the desired version
  • Verifies the final implementation using the standard ERC-1967 implementation slot
    (0x360894a13ba1a3210667c828492db98dca3e2076cc3735a920a3ca505d382bbc)

Tests

• Extend ServiceProviderRegistryTest to cover:
  • testAnnouncePlannedUpgrade — happy-path announce and gated upgrade flow
  • testAnnouncePlannedUpgradeOnlyOwner — only the owner can announce
  • testAnnouncePlannedUpgradeInvalidImplementation — revert on non-contract implementation
  • testAnnouncePlannedUpgradeInvalidEpoch — revert when afterEpoch <= block.number
  • testOnlyOwnerCanUpgrade — validates that:
    • Non-owner upgrades revert
    • Owner can upgrade after a valid announcement and epoch gating

Closes : #355