rename: "Team" billing tier to "Family"

All literal "team" tier-value references renamed to "family" across
API routes, admin UI, OpenAPI schemas, and lib/tiers.ts. The DB enum
value itself is renamed in place via ALTER TYPE ... RENAME VALUE
(migration 0044) rather than drizzle-kit's auto-generated
drop-and-recreate-the-enum migration, which would have failed against
any existing row still holding 'team' — RENAME VALUE preserves
existing data with no cast/backfill needed.

Also adds STRIPE_PLAN.md — a full Stripe billing integration plan
(Checkout+Portal, tier→Price mapping, admin billing dashboard, and a
multi-user Family-group design since Family is meant to cover several
accounts under one subscription, not one payer). Planning only, no
Stripe code yet.

v0.47.0

apps/web/app/api/v1/ai/regenerate/route.ts

@@ -47,7 +47,7 @@ export async function POST(req: NextRequest) {
 
   const { instruction, language, ...current } = parsed.data;
 
-  const result = await withAiQuota(session!.user.id, session!.user.tier as "free" | "pro" | "team", () =>
+  const result = await withAiQuota(session!.user.id, session!.user.tier as "free" | "pro" | "family", () =>
     regenerateRecipe(current, instruction, { ...aiConfig, language }), { skipQuota: aiConfig.isByok }
   );
   if (!result.ok) return result.response;