docs: add Analog gateway SSE guide

[benpsnyder]

Summary

• Adds a standalone Analog how-to for running a server-owned SpacetimeDB TypeScript SDK connection behind an Analog app.
• Shows server-side page loading, Nitro/h3 API routes for mutations and SSE, an Angular EventSource service, and a CLI smoke test.
• Links the guide from the Developer Resources index.

Why

Issue #5004 is tracking the app-server gateway architecture for teams that need application-owned auth, tenant policy, enterprise identity, and server-side testability while still consuming realtime SpacetimeDB updates in browser apps. The previous gateway guide covers the generic and TanStack Start shape; this PR adds the Analog/Angular variant without requiring a stacked branch.

Validation

• git diff --check
• pnpm --dir docs typecheck
• pnpm --dir docs build

The docs build still reports the existing docusaurus-plugin-llms-txt warning for /docs/ask-ai/ask-ai; the build completes successfully.

[cloutiertyler]

Hi @benpsnyder, thanks for your contribution to the docs. We don't accept draft PRs in our repo to keep our PRs relatively neat and manageable, so I'm going to close this for now, at least until you have a complete PR for us to review.