[codex] add generated project wiki

[Che-Zhu]

Summary

Add a generated repository-local wiki under docs/wiki/ for the current Next.js codebase.

What Changed

• added wiki entry pages for architecture, routing, rendering, auth, config, data models, integrations, and background jobs
• added API domain pages and business-domain feature pages
• added a machine-readable manifest with source mappings
• added a todo.md page for code-backed follow-up items surfaced during wiki generation

Why

The repository had architecture and operational documentation, but it did not have a code-driven wiki that maps current routes, APIs, runtime boundaries, and feature domains into a single navigable doc set.

Impact

• gives developers and agents a faster onboarding path into the current codebase
• makes API and domain boundaries easier to inspect from one place
• records a few obvious navigation and architecture follow-ups without mixing them into the main architecture page

Validation

• jq . docs/wiki/_meta/manifest.json
• reviewed generated docs/wiki/ structure and linked index pages

[github-actions]

✅ PR Check Results: Passed

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  Commit: c199a29b53e3520c2c1cc29325108a28bc6d2698
  Branch: codex/wiki-docs

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