feat: added gcp-nation deployment branch with sqlite backend

[evanpetzoldt]

This pull request introduces a new deployment architecture for SyncBot targeting the Nation's GCP infrastructure on Cloud Run using SQLite with Litestream for continuous backup to Google Cloud Storage (GCS). It adds comprehensive infrastructure-as-code, deployment automation, and documentation for the "F3 Nation" environment. The changes enable single-instance, stateless deployment with automated backups, disaster recovery, and a streamlined CI/CD pipeline via GitHub Actions.

Key changes include:

Deployment Automation & CI/CD:

• Added a new GitHub Actions workflow (.github/workflows/deploy-nation.yml) to automate building, pushing, and deploying the SyncBot Docker image to Cloud Run on pushes to nation-staging or nation-prod branches. This workflow uses Workload Identity Federation for secure authentication and is fully environment-variable driven.

Containerization & Runtime Environment:

• Introduced a new Dockerfile (infra/gcp-nation/Dockerfile) tailored for the Nation deployment, which installs Python, system dependencies, Litestream for SQLite replication, and sets up the entrypoint and application code for Cloud Run.
• Added an entrypoint script (infra/gcp-nation/entrypoint.sh) that restores the SQLite database from GCS on cold start, starts Litestream replication in the background, and launches the app.
• Added a Litestream configuration file (infra/gcp-nation/litestream.yml) for continuous SQLite WAL streaming to GCS.

Infrastructure Configuration & Documentation:

• Provided an example Terraform variables file (infra/gcp-nation/example.tfvars) to simplify per-environment configuration and clarify required settings for staging and production.
• Added a Terraform provider lockfile (infra/gcp-nation/.terraform.lock.hcl) to ensure reproducible infrastructure builds.

Comprehensive Deployment Guide:

• Added a detailed deployment guide (infra/gcp-nation/DEPLOY.md) covering architecture, prerequisites, step-by-step setup (Slack, GCP, Terraform, GitHub Actions), backup/recovery, troubleshooting, and cost estimates for the new Nation deployment.