feat(admin-tags): POST /api/admin/tags to create craft/cooperative tags

Admin-only route that validates a label + pool via zod, slugifies the
label, returns the existing tag if the slug already exists, otherwise
creates a new active Tag document.

server/utils/schemas.js

@@ -383,6 +383,11 @@ export const tagSuggestionSchema = z.object({
   pool: z.enum(['craft', 'cooperative'])
 })
 
+export const adminTagCreateSchema = z.object({
+  label: z.string().trim().min(1).max(100),
+  pool: z.enum(['craft', 'cooperative'])
+})
+
 // --- Board post / channel schemas ---
 
 export const boardPostCreateSchema = z.object({