Bump v2 production dependencies and Go 1.25 CI

[dependabot]

Summary

This PR updates the v2 production dependency group and the CI needed to validate that dependency set.

Changed areas:

• v2: production dependency updates in go.mod / go.sum, plus small lint cleanups required by the newer lint toolchain.
• .github/workflows: build and lint workflows updated to run with Go 1.25.x and current GitHub Action versions.

Why CI changed

The updated dependency graph now includes modules whose own go directive requires Go 1.25.0, including Azure SDK, OpenTelemetry, and golang.org/x/* modules. Running the PR with the previous Go 1.21 workflow setup caused the gates to fail even though the dependency update builds and tests with Go 1.25.

The linter workflow was also updated to golangci-lint v2.12.2, which surfaced two small cleanup items:

• Use reflect.Pointer instead of the old reflect.Ptr alias.
• Remove an ineffective break from the processor cancellation select; behavior is unchanged because the surrounding loop exits via ctx.Err() != nil.

Validation

• go build -v ./...
• go test -count=1 -coverprofile=/tmp/go-shuttle-v2-profile.cov ./...
• golangci-lint v2.12.2 run
• GitHub Actions checks are passing on the latest pushed commit.

[karenychen]

Follow-up on the CI changes in this branch:

• The workflow Go version was moved to 1.25.x because the updated dependency graph now includes modules whose own go directive is 1.25.0 (azcore, OpenTelemetry, and golang.org/x/*). Keeping Actions on Go 1.21 caused the previous coverage/linter failures once the module target moved to Go 1.25.
• The processor.go cleanup is only to satisfy the newer linter. The old break inside case <-ctx.Done() only broke out of the select, not the outer for; behavior still exited on the next loop condition because ctx.Err() was non-nil. I removed that ineffective break rather than adding a labeled loop, so the cancellation behavior stays the same and the control flow is clearer.

Local validation after the change:

• go build -v ./...
• go test -count=1 -coverprofile=/tmp/go-shuttle-v2-profile.cov ./...
• golangci-lint v2.12.2 run