Add Helm chart CI, release packaging, and operator docs

[NickCrew]

Description

Close the Helm packaging milestone with the validation, release, and docs path operators need. The implementation should make chart regressions visible in CI and give users a clear install path for Kubernetes without losing the existing hosted/static UI story.

If chart publishing is not ready to automate, document the chosen release channel and file a follow-up for automation rather than leaving the process implicit.

Acceptance Criteria

• Migrate synapse-waf to Rust 2024 edition #1 CI lints, templates, and packages all Helm charts on pull requests
• Cache parsed EvalContext data across body-phase and deferred WAF passes #2 Release workflow publishes chart artifacts to the selected channel or documents the manual release command
• Instantiate and integrate HeaderProfiler for per-endpoint header anomaly detection #3 Operator docs cover install, upgrade, rollback, migrations, secrets, ingress/WebSocket notes, metrics, and production dependency guidance
• Escalate invalid-session weight non-linearly to catch faster brute-force #4 Docs describe where Vercel/static UI hosting fits when the Kubernetes cluster hosts the Fleet API

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Migrated from backlog TASK-103.6 (synapse).