docs: Expand deployment guide (CI/CD, GCP, read/write separation, cluster-sidecar) (#1651) * docs: Add CI/CD deployment section with GitHub Actions guide Adds a starter CI/CD page covering the spice-cloud-deploy-action GitHub Action for Spice Cloud Platform deployments and pointers to the existing Argo CD and Flux GitOps guides for self-hosted Kubernetes. Refs #1049 * ci: trigger fresh CI run * Add GCP integrations documentation and deployment guides - Introduced a new document for GCP integrations detailing data connectors, AI models, embeddings, and authentication methods. - Updated the main deployment guide to include GCP as a deployment target and outlined deployment architectures. - Added a new guide for read/write separation to optimize data ingestion and querying workloads. - Created a cluster-sidecar architecture document to explain the benefits and considerations of this deployment model. - Updated snapshots documentation to reference the new read/write separation guide and clarified configuration options. * fix: update tags in read/write separation documentation to reflect Kubernetes and Helm * fix: update links in GCP deployment and read/write separation documentation for consistency * fix: remove unnecessary semicolon in hybrid architecture documentation --------- Co-authored-by: claudespice <claudespice@users.noreply.github.com> Co-authored-by: Luke Kim <80174+lukekim@users.noreply.github.com>