feat: developer access permission gates webhooks/API keys/BYOK (v0.71.0)

Webhooks, self-serve API keys, and BYOK AI provider keys had zero
access gating -- any logged-in user, any tier. Adds users.isDeveloper
(boolean, admin-toggled in admin/users/[id] alongside role/tier),
checked via a single hasDeveloperAccess() (lib/permissions.ts) so a
future subscription-tier auto-grant is a one-line change there, not
a redesign across call sites.

requireDeveloper() (lib/api-auth.ts) wraps requireSession() with a
fresh isDeveloper check (same reasoning as requireAdmin re-querying
role: session.user's cookieCache can be up to 5 minutes stale) and
replaces requireSession in all 8 gated routes: webhooks CRUD +
deliveries + redeliver, api-keys CRUD, ai-keys CRUD.

Settings UI: the sidebar hides API Keys/Webhooks nav entries for
non-developers; those pages and the BYOK section of Settings -> AI
show a locked notice instead of the manager component when accessed
directly.

Migration grandfathers in anyone who already has a webhook, API key,
or BYOK key row -- ships as a new gate on existing features, not a
silent lockout of active integrations.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/web/lib/api-auth.ts

@@ -4,6 +4,7 @@ import { NextRequest, NextResponse } from "next/server";
 import { auth } from "@/lib/auth/server";
 import { db, apiKeys, users, eq } from "@epicure/db";
 import { applyRateLimit } from "@/lib/rate-limit";
+import { hasDeveloperAccess } from "@/lib/permissions";
 
 export async function requireSession() {
   const session = await auth.api.getSession({ headers: await headers() });
@@ -39,6 +40,29 @@ export async function requireAdmin(opts?: { allowModerator?: boolean }) {
   return { session, response: null };
 }
 
+/** Gates webhooks, self-serve API keys, and BYOK routes behind
+ * users.isDeveloper — re-queried fresh for the same reason requireAdmin
+ * re-queries role (session.user's cookieCache can be up to 5 minutes
+ * stale, e.g. right after an admin grants access). */
+export async function requireDeveloper() {
+  const { session, response } = await requireSession();
+  if (response) return { session: null, response };
+
+  const [dbUser] = await db
+    .select({ isDeveloper: users.isDeveloper })
+    .from(users)
+    .where(eq(users.id, session!.user.id))
+    .limit(1);
+
+  if (!dbUser || !hasDeveloperAccess(dbUser)) {
+    return {
+      session: null,
+      response: NextResponse.json({ error: "Developer access required — ask an admin to enable it" }, { status: 403 }),
+    };
+  }
+  return { session, response: null };
+}
+
 type SessionLike = {
   user: {
     id: string;