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/components/admin/user-editor.tsx

@@ -15,12 +15,12 @@ import { Label } from "@/components/ui/label";
 interface UserEditorProps {
   userId: string;
   currentRole: "user" | "moderator" | "admin";
-  currentTier: "free" | "pro" | "team";
+  currentTier: "free" | "pro" | "family";
 }
 
 export function UserEditor({ userId, currentRole, currentTier }: UserEditorProps) {
   const [role, setRole] = useState<"user" | "moderator" | "admin">(currentRole);
-  const [tier, setTier] = useState<"free" | "pro" | "team">(currentTier);
+  const [tier, setTier] = useState<"free" | "pro" | "family">(currentTier);
   const [saving, setSaving] = useState(false);
 
   async function handleSave() {
@@ -68,7 +68,7 @@ export function UserEditor({ userId, currentRole, currentTier }: UserEditorProps
             <SelectContent>
               <SelectItem value="free">Free</SelectItem>
               <SelectItem value="pro">Pro</SelectItem>
-              <SelectItem value="team">Team</SelectItem>
+              <SelectItem value="family">Family</SelectItem>
             </SelectContent>
           </Select>
         </div>