Wes/core architecture rework - #2638

Adds five new draft MDX pages (server-overview, server-database,
server-middleware, server-plugins, server-routes) and an Agents
placeholder, wired into the nav under a draft Server group. Pages
are hidden in production and visible with VITE_SHOW_DRAFTS=true.

Includes nav keys in all locale files and an updated i18n doc-coverage
baseline to exempt draft pages from the localized-doc requirement.

Reframes db.ts as optional rather than default, moves the database
plugin section after auth and agent-chat, expands the intro to explain
what plugins are and how Nitro discovers them, and adds a new section
on writing custom plugins with defineNitroPlugin linking to Nitro docs.

…are guide

Expands the draft from a stub into a full page:
- Adds a diagram showing callers → middleware → allowed/blocked outcomes
- Rewrites the intro to describe middleware as a general cross-cutting layer
- Adds a "Writing Middleware" section with a defineEventHandler example and
  links to Nitro/H3 docs, placed before the auth section
- Consolidates The Auth Guard, Why Middleware, and Adding Public Paths under
  a single "The Auth Middleware" H2 with those as H3 subheadings

…agram

Reorganizes the draft from a loosely ordered reference into a narrative
that builds from concept to implementation:
- New diagram showing Browser/UI and Agent loop reaching the database
  through the same Actions layer
- Hosting Options section covering all five backends in order of
  complexity (SQLite default, PGlite, Postgres, Turso, Builder managed)
- Setting Up section as four numbered steps: define schema, create DB
  client, write migrations, query in actions
- Scoping Data to Users consolidates the owner_email and ownableColumns
  patterns that were previously scattered
- Removes all em-dashes throughout in favor of separate sentences

Ports the sync loop content from the published server.mdx into the
database page, where it completes the write story: after an action
mutates data, the sync version increments and useDbSync() on the client
invalidates caches so the UI refreshes. Includes the sync loop diagram
and the poll endpoint block. Adds a What's next link to real-time-sync.

Splits server.mdx into five pages (overview, database, middleware,
plugins, routes), un-drafts them in the nav, and repoints cross-page
links across the docs that pointed at the old combined page.

Translates the 5 server-*.mdx docs (overview, database, middleware,
plugins, routes) into ar-SA, de-DE, es-ES, fr-FR, hi-IN, ja-JP, ko-KR,
pt-BR, zh-CN, and zh-TW, replacing verbatim English copies left over
from the Server section split.

- Remove the old single-page server.mdx from every locale; it has no
  English source counterpart since the split and was unreachable.
- Translate the Server dropdown's sidebar labels (Overview, Middleware,
  Plugins, Routes, and Server itself for ar-SA/hi-IN) so the nav
  structure matches across locales.
- Fix a stale content/server.md reference in docs/AGENTS.md.
- Drop 50 now-stale entries from the doc-coverage baseline and add
  "Agent Native" to the no-translate-terms allowlist so the guard
  no longer flags the brand name as an untranslated string.

- Point the Real-Time Sync link at the existing key-concepts#polling-sync
  anchor instead of the non-existent /docs/real-time-sync slug.
- server-database.mdx copied its diagram/AnnotatedCode/DataModel blocks
  from database.mdx without regenerating their ids, so three blocks
  collided with database.mdx's own blocks of the same id. Assign each
  a unique id.

Applies to the English source and all 10 locale translations, which
mirrored the same bugs.