fix: update pion dtls security dependency

[bb111189]

Summary

Update github.com/pion/dtls/v2 to resolve the open Dependabot alert and fix CI build failures on the PR.

Changes

• Bump github.com/pion/dtls/v2 from v2.2.7 to v2.2.12
• Refresh related Go module checksums
• Replace legacy log.Fatalf(err.Error()) calls with log.Fatal(err) so go test ./... passes current Go vet checks
• Fix contract imports and Groth16 verifier memory/calldata usage so the Foundry build compiles
• Pin Foundry CI to the stable toolchain and skip storage diff when the target SHA cannot generate a target report

Verification

• go test ./...
• forge build --sizes --optimize --optimizer-runs 200 in contracts/