Admin project CRUD: full editor, featured toggle, GitHub-or-FS storage

What was done

Built the admin surface for managing /content/projects/{en,ko}/*.mdx files end-to-end, without leaving the browser:

• /admin/projects — list view, sorted featured-first, with per-row featured toggle, edit, view, and delete actions.
• /admin/projects/new — full ProjectEditor covering every frontmatter field: title, description, date, locale, slug, status, featured, url (required — the live link), repo, stack, tags, role, translationKey.
• /admin/projects/[locale]/[slug]/edit — same editor pre-filled from the existing mdx.
• API: POST /api/admin/projects (create) and PUT / DELETE /api/admin/projects/[locale]/[slug] (update / remove).
• lib/project-storage.ts — new storage helper mirroring the post-storage pattern: when GitHub is configured (githubConfigured() true) it commits via the Contents API, otherwise it writes to the local filesystem.
• AdminNav gains a "Projects" link between Posts and Distribution.

The featured cap is shown in the header as n/3 but not enforced server-side — the home page's getFeaturedProjects already slices the top-3 by date, so over-selection in the admin is cosmetic.

Why it was needed

Original rationale not in commit; reconstructed from diff. Until this commit, projects were authorable only by hand-editing mdx files in the repo. Posts already had lib/storage.ts + an admin editor, so projects were the last content type lagging behind. The new helper mirrors the post path exactly, which preserves the dev-vs-prod write split documented in docs/architecture.md (never fs.writeFile in production — see the EROFS entry in troubleshooting).

Files / functions changed

• app/(admin)/admin/projects/page.tsx — list page.
• app/(admin)/admin/projects/new/page.tsx — create page wrapping ProjectEditor.
• app/(admin)/admin/projects/[locale]/[slug]/edit/page.tsx — edit page, pre-fills ProjectEditor.
• app/api/admin/projects/route.ts — POST (create). Validates locale via isLocale, slug via isValidSlug, requires title/description/url/body, refuses if file already exists (409), defaults status to active, calls revalidatePath for /, /ko, /projects, /ko/projects, the specific project pages, and /admin/projects.
• app/api/admin/projects/[locale]/[slug]/route.ts — PUT (update) + DELETE.
• components/admin/ProjectsList.tsx — list + inline featured toggle + delete.
• components/admin/ProjectEditor.tsx — shared form.
• components/admin/AdminNav.tsx — adds "Projects" tab.
• lib/project-storage.ts — projectFileExists, serializeProjectMdx (drops undefined keys before matter.stringify), saveProject, deleteProject. GitHub branch via commitFile / deleteFile; local branch via fs.writeFile / fs.unlink under process.cwd().

Net: +855 lines across 9 files, all new (no existing files modified beyond AdminNav.tsx).

Result / verification

Commit landed in main. No verification artifacts attached to this commit (no follow-up test entry, no screenshots). The storage helper is a near-copy of lib/storage.ts, which is exercised by the post admin flow, so the prod-vs-dev branching is the same shape that already works.

Open / what didn't get done

• Featured cap is advisory in the UI, not enforced in POST / PUT. Could allow more than 3 featured projects to exist on disk; the home page silently truncates.
• No admin UI for editing project log entries (cross-repo or repo-local). Mdx still hand-written, as called out later in the cross-repo aggregation entry from the same day.
• This commit slipped past the project-log dual-write convention — no [no-log] and no log entry at the time. This entry is the backfill.

Commit — 9d1972a