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/meal-plan/generate/route.ts

@@ -75,7 +75,7 @@ export async function POST(req: NextRequest) {
     }
   }
 
-  const result = await withAiQuota(userId, session!.user.tier as "free" | "pro" | "team", () =>
+  const result = await withAiQuota(userId, session!.user.tier as "free" | "pro" | "family", () =>
     generateMealPlan(
       {
         dietaryPrefs: parsed.data.dietaryPrefs,
@@ -99,7 +99,7 @@ export async function POST(req: NextRequest) {
   let chargedRecipes = 0;
   try {
     for (let i = 0; i < plan.entries.length; i++) {
-      await checkAndIncrementTierLimit(userId, session!.user.tier as "free" | "pro" | "team", "recipe");
+      await checkAndIncrementTierLimit(userId, session!.user.tier as "free" | "pro" | "family", "recipe");
       chargedRecipes++;
     }
   } catch (err) {