refactor(charts): split Service/PVC files + unify schema $defs (tier-2)

[somaz94]

Summary

Tier-2 structural cleanup across the four workload charts (mysql, postgresql, redis, buildkit). Rendered output is unchanged — this is a pure refactor.

#1 — Split Service / PVC into dedicated template files

• mysql / postgresql / redis: deployment.yaml → Service moved to service.yaml, PVC moved to pvc.yaml (one file per kind).
• buildkit: statefulset.yaml → Service moved to service.yaml. The PVC stays inline as volumeClaimTemplates (it is not a separate top-level resource), so no pvc.yaml.

#2 — Hoist shared shapes into schema $defs

• service: inline in all four (byte-identical) → promoted to $defs.service + $ref.
• persistence: mysql/postgresql already used $defs; redis (base + mountPath) and buildkit (base − existingClaim + mountPath) promoted from inline to $defs.persistence + $ref, each keeping its own shape.
• $defs order unified to metadataBlock / resources / service / persistence.

Verification

• Render-equivalence: helm template (persistence on/off × 4 charts = 8 combos) is byte-identical to main after stripping the # Source: path comments.
• Schema behavior-neutral: recursively resolving $ref yields a schema identical to the original inline schema; JSON well-formed.
• make lint / make template / make validate (kubeconform) green for all four; helm package tarballs include the new files.

Version bumps

chart	version
mysql	0.1.1 → 0.1.2
postgresql	0.1.1 → 0.1.2
redis	0.1.1 → 0.1.2
buildkit	0.1.2 → 0.1.3

CHANGELOG + artifacthub.io/changes updated per chart. Merge triggers release.yml auto-release.

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