feat(api): tiered cumulative quota + self-service registration

Anonymous callers get a free cumulative quota (1000 calls per IP); once
exhausted they get 403 quota_exhausted and must register. Public users can
self-register (email+password) to obtain a higher-quota API key, view usage,
and regenerate the key. Quota counters live in Redis; the public API stays
read-only except for the registration writes.

- migration 0011: app_user table + api_key.quota_total + 'registered' tier
- ratelimit: IncrTotal/TotalUsed/CopyTotal lifetime counters
- middleware: enforce cumulative quota + X-Quota-* headers
- store: RegisterUser/Authenticate/RegenerateKey (bcrypt)
- handlers: POST /api/v1/register, /account, /account/regenerate
- admin: quota_total column + registered tier
- public: 'API 密钥' account page + API docs quota section

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

public-frontend/src/App.tsx

@@ -1,16 +1,18 @@
 import { useEffect, useState } from "react";
-import { Boxes, Search, PlusCircle, Code2 } from "lucide-react";
+import { Boxes, Search, PlusCircle, Code2, KeyRound } from "lucide-react";
 import Home from "./components/Home";
 import ProductView from "./components/ProductView";
 import Contribute from "./components/Contribute";
 import ApiDocs from "./components/ApiDocs";
+import Account from "./components/Account";
 import { api } from "./api";
 
 type View =
   | { name: "home" }
   | { name: "product"; id: string }
   | { name: "contribute" }
-  | { name: "api" };
+  | { name: "api" }
+  | { name: "account" };
 
 export default function App() {
   const [view, setView] = useState<View>({ name: "home" });
@@ -59,6 +61,14 @@ export default function App() {
             >
               <Code2 className="w-4 h-4" /> API
             </button>
+            <button
+              className={`px-3 py-1.5 rounded-md flex items-center gap-1.5 ${
+                view.name === "account" ? "bg-emerald-50 text-emerald-700" : "text-gray-600 hover:bg-gray-100"
+              }`}
+              onClick={() => setView({ name: "account" })}
+            >
+              <KeyRound className="w-4 h-4" /> API 密钥
+            </button>
           </nav>
         </div>
       </header>
@@ -77,7 +87,8 @@ export default function App() {
         {view.name === "contribute" && (
           <Contribute onDone={() => setView({ name: "home" })} />
         )}
-        {view.name === "api" && <ApiDocs />}
+        {view.name === "api" && <ApiDocs onRegister={() => setView({ name: "account" })} />}
+        {view.name === "account" && <Account />}
       </main>
 
       <footer className="border-t bg-white">