Remove Dagger workflows

[marccampbell]

Summary

• remove the Dagger configuration, Go module, generated workflow sources, and Dependabot entry
• replace validation, migration rendering, image builds, and staged/production releases with Make targets, Bash scripts, and native Dockerfiles
• make the native validation path deterministic by gating the live Anthropic test and correcting stale test expectations and the Next.js route parameter type
• refuse to replace an existing release tag, avoiding the old destructive tag-rewrite behavior

Validation

• make validate
• ./scripts/build-images.sh test
• docker build --check -f Dockerfile.worker .
• docker build --check -f chartsmith-app/Dockerfile chartsmith-app
• worker image smoke tests for Helm 3.17.0, bootstrap assets, and CLI startup
• local staging Kustomize render with the generated migration manifest and both image substitutions
• residual repository scan confirms there are no remaining Dagger references