feat(core): dynamic custom frontmatter fields for CTF writeup metadata

- Add extra_fields JSONB column to documents table (migration 0003)
- CreateDocInput/UpdateDocInput: extraFields?: Record<string, string>
- parseFile: extracts non-standard frontmatter keys as extraFields
- stringifyFile: writes extraFields dynamically to YAML frontmatter
- toMeta: spreads extraFields from DB row into DocumentMeta
- DocForm: '+ Add field' UI for content creators to add any metadata
- API routes: splitPayload() separates standard vs custom fields
- Doc page: CustomFieldBadges dynamically renders any custom field
- Add db:migrate / db:push scripts + deploy workflow migration step
- Add CTF writeup template (content/writeups/ctf/template/)
- Add sample DEF CON writeup with event/challenge/category/difficulty/points
- Add @tailwindcss/typography for table rendering (prose classes)
- Add remark-gfm for GitHub Flavored Markdown table parsing

packages/types/src/index.ts

@@ -14,6 +14,15 @@ export interface DocumentMeta {
   path: string; // relative path under content/
   createdAt: string; // ISO
   updatedAt: string; // ISO
+  // CTF writeup metadata (optional — only set for writeups)
+  event?: string;
+  challenge?: string;
+  category?: string;
+  difficulty?: "easy" | "medium" | "hard";
+  points?: number;
+  // Dynamic custom frontmatter fields (serialized as-is to YAML frontmatter).
+  // Allows content creators to add arbitrary metadata keys without code changes.
+  extraFields?: Record<string, string>;
 }
 
 export interface Document extends DocumentMeta {