feat: add Team billing tier

Widens the tier enum from free/pro to free/pro/team and every
"free" | "pro" cast that assumed exactly two tiers (~30 call sites:
every AI route's withAiQuota/checkAndIncrementTierLimit call, admin
user/invite management, upload quota checks, OpenAPI schemas). Team
sits above Pro with genuinely unlimited recipes/public-recipes (the
-1 sentinel, which Pro doesn't actually use — Pro uses large finite
numbers instead) and a higher AI-call/storage cap. Seeded via
db:seed, editable afterward from Admin > Tiers.

role (user/moderator/admin — permissions) and tier (free/pro/team —
billing limits) stay separate concepts, as they already were; this
does not touch role-based permissions.

Requires migration 0043 to run against a live DB — not applied in
this sandbox (no Docker here); run `pnpm db:migrate` then `pnpm db:seed`.

v0.44.0

apps/web/app/api/v1/ai/variations/[id]/route.ts

@@ -47,7 +47,7 @@ export async function POST(req: NextRequest, { params }: Params) {
   if (!configResult.ok) return configResult.response;
   const aiConfig = configResult.data;
 
-  const result = await withAiQuota(session!.user.id, session!.user.tier as "free" | "pro", () =>
+  const result = await withAiQuota(session!.user.id, session!.user.tier as "free" | "pro" | "team", () =>
     suggestVariations(
       {
         title: recipe.title,