Replace Strapi CMS with PocketBase

Strapi + Postgres are gone in favor of PocketBase: a single Go binary
with embedded SQLite, built-in admin UI and per-collection API rules.
No content existed yet, so this is a clean swap with no data migration.

Collections and rules are defined as code in pocketbase/pb_migrations/
and applied automatically on first boot. Draft & Publish has no native
PocketBase equivalent, so it's reproduced with a nullable `publishedAt`
field enforced by listRule/viewRule, matching the old Strapi semantics.

Routing flips: PocketBase's admin UI and REST/file API are hardwired to
`/_/` and `/api/*` at the domain root (its own dashboard assets and API
calls reference those paths directly, so a stripped path prefix like
`/admin/*` would break them). `/api` is therefore reserved for
PocketBase now, and the frontend's Nitro endpoints move to `/content/*`
(frontend/server/routes/content/, not server/api/). A `/admin` vanity
route in Nitro (not Caddy) redirects to `/_/`, so it works the same in
dev, where Caddy isn't part of the stack, and in production.

frontend/server/utils/strapi.ts becomes pocketbase.ts; queries.ts is
rewritten for PocketBase's filter/sort/fields/expand query syntax.
StrapiImage becomes MediaImage (no width/height — PocketBase file
fields don't store dimensions, and the cover images already reserve
their aspect ratio via CSS, so this is not a regression).

docs/*.md, CLAUDE.md and README.md are updated in the same commit.

frontend/server/routes/content/articles/[slug].get.ts

@@ -0,0 +1,42 @@
+import type { Article, Category } from '#shared/types/blog'
+
+interface RawArticle {
+  id: string
+  title: string
+  slug: string
+  publishedAt: string
+  content: string | null
+  cover: string
+  coverAlt: string | null
+  authorName: string | null
+  expand?: { category?: Category }
+}
+
+export default defineEventHandler(async (event): Promise<Article> => {
+  const slug = getRouterParam(event, 'slug')
+
+  if (!slug) {
+    throw createError({ statusCode: 400, statusMessage: 'Missing article slug' })
+  }
+
+  const response = await pbFetch<PbList<RawArticle>>(
+    `/api/collections/articles/records?fields=${ARTICLE_DETAIL_FIELDS}&expand=category&filter=${encodeURIComponent(`slug = ${quote(slug)}`)}&${pagination(1, 1)}`
+  )
+
+  const article = response.items[0]
+
+  if (!article) {
+    throw createError({ statusCode: 404, statusMessage: 'Article not found' })
+  }
+
+  return {
+    title: article.title,
+    slug: article.slug,
+    publishedAt: article.publishedAt,
+    cover: toMediaImage('articles', article.id, article.cover, article.coverAlt),
+    category: article.expand?.category ?? null,
+    html: renderMarkdown(article.content),
+    summary: summarise(article.content),
+    author: article.authorName || null,
+  }
+})