docs(cloud): Reframe PAT and deployment hooks as concepts, non-Dart files as a guide

[developerjamiu]

Summary

Moves three pages out of `cloud_docs/reference/` into their correct content types per the Cloud IA. Adds redirects from old URLs and repoints inbound links from the Deployments concept and auth CLI reference.

• Personal access tokens → concept at `/cloud/concepts/personal-access-tokens`. Env-var-first framing for CI; corrected `serverpod_cloud_deploy` repo reference (was incorrectly hyphenated and 404'd); caution callout on one-time token visibility.
• Deployment hooks → concept at `/cloud/concepts/deployment-hooks`. Covers pre/post lifecycle timing, sequential execution, environment-variable inheritance, and the pre/post failure asymmetry (warning callout).
• Static assets → reframed as a guide at `/cloud/guides/ship-non-dart-files`. Originally planned as a concept; reclassified to guide during drafting because Cloud has no asset-handling capability to model. The page is procedural; the four file-type patterns (config, templates, CSV, binary) are the substance.

Test plan

• Build passes (`npm run build`)
• Redirects work: `/cloud/reference/personal-access-tokens` → concept; `/cloud/reference/deployment/assets` → guide; `/cloud/reference/deployment/deployment-hooks` → concept.
• Inbound link from Deployments concept to all three new pages resolves.
• Inbound link from `scloud auth` CLI reference to the PAT concept resolves.