fix: reject zero scale factor

[prd-carapulse]

Summary

• Reject zero SCALE_FACTOR values after the constructor's integer division.
• Add a Certora harness/spec proving scaleFactorCannotBeZero for every successful MorphoChainlinkOracleV2 deployment.
• Add a Certora GitHub Actions workflow plus a focused Forge regression test for a config that previously rounded the scale factor to zero.

Request Context

• Initiator: Mathis / Slack: <@U02NB58F6R3> / GitHub: @MathisGD
• Initial Slack thread: C0B520ZTPJM / 1781506867.952699
• Additional context: requested a PR in morpho-org/morpho-blue-oracles to prove with Certora that the scale factor cannot be zero.
• Rationale: prevent successful oracle deployments with a zero price scale factor.

Test Plan

• forge fmt --check
• forge build --force
• forge build --contracts certora/helpers/MorphoChainlinkOracleV2Harness.sol --force
• forge test --match-path test/MorphoChainlinkOracleV2ScaleFactorTest.sol -vvv
• certoraCVLFormatter certora/specs/MorphoChainlinkOracleV2.spec
• jq < certora/confs/MorphoChainlinkOracleV2.conf
• certoraRun certora/confs/MorphoChainlinkOracleV2.conf --compilation_steps_only
• Certora GitHub Actions workflow remote proof with CERTORAKEY

Requested by: <@U02NB58F6R3>