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/lib/tiers.ts

@@ -35,12 +35,12 @@ export class TierLimitError extends Error {
  */
 export async function checkAndIncrementTierLimit(
   userId: string,
-  fallbackTier: "free" | "pro" | "team",
+  fallbackTier: "free" | "pro" | "family",
   key: "recipe" | "aiCall" | "storage",
   amount = 1
 ): Promise<void> {
   const [dbUser] = await db.select({ tier: users.tier }).from(users).where(eq(users.id, userId));
-  const userTier = (dbUser?.tier as "free" | "pro" | "team" | undefined) ?? fallbackTier;
+  const userTier = (dbUser?.tier as "free" | "pro" | "family" | undefined) ?? fallbackTier;
 
   const [tierDef] = await db
     .select()