Add user authentication with login/register

- Add users and sessions tables to database schema
- Add bcryptjs for password hashing
- Create auth API routes (login, register, logout, me)
- Add AuthProvider context for client-side auth state
- Update all API routes to require authentication and filter by userId
- Create login and register pages
- Add AppShell component for authenticated layout
- Update all pages to use AppShell and show user info
- Each user now has their own private entries and tags

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/app/login/page.tsx

@@ -0,0 +1,108 @@
+"use client";
+
+import { useState } from "react";
+import { useRouter } from "next/navigation";
+import Link from "next/link";
+import { Loader2 } from "lucide-react";
+import { APP_NAME } from "@/lib/constants";
+
+export default function LoginPage() {
+  const router = useRouter();
+  const [email, setEmail] = useState("");
+  const [password, setPassword] = useState("");
+  const [error, setError] = useState("");
+  const [isLoading, setIsLoading] = useState(false);
+
+  const handleSubmit = async (e: React.FormEvent) => {
+    e.preventDefault();
+    setError("");
+    setIsLoading(true);
+
+    try {
+      const res = await fetch("/api/auth/login", {
+        method: "POST",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({ email, password }),
+      });
+
+      const data = await res.json();
+
+      if (!res.ok) {
+        setError(data.error || "Login failed");
+        return;
+      }
+
+      router.push("/");
+      router.refresh();
+    } catch {
+      setError("An error occurred");
+    } finally {
+      setIsLoading(false);
+    }
+  };
+
+  return (
+    <div className="min-h-screen flex items-center justify-center px-4">
+      <div className="w-full max-w-sm">
+        <div className="text-center mb-8">
+          <h1 className="text-2xl font-light mb-2">{APP_NAME}</h1>
+          <p className="text-muted">Sign in to your account</p>
+        </div>
+
+        <form onSubmit={handleSubmit} className="space-y-4">
+          {error && (
+            <div className="p-3 bg-red-500/10 border border-red-500/20 rounded-lg text-red-400 text-sm">
+              {error}
+            </div>
+          )}
+
+          <div>
+            <label htmlFor="email" className="block text-sm text-muted mb-1">
+              Email
+            </label>
+            <input
+              id="email"
+              type="email"
+              value={email}
+              onChange={(e) => setEmail(e.target.value)}
+              required
+              className="w-full px-4 py-3 bg-surface border border-border rounded-lg focus:outline-none focus:border-muted"
+              placeholder="you@example.com"
+            />
+          </div>
+
+          <div>
+            <label htmlFor="password" className="block text-sm text-muted mb-1">
+              Password
+            </label>
+            <input
+              id="password"
+              type="password"
+              value={password}
+              onChange={(e) => setPassword(e.target.value)}
+              required
+              className="w-full px-4 py-3 bg-surface border border-border rounded-lg focus:outline-none focus:border-muted"
+              placeholder="Enter your password"
+            />
+          </div>
+
+          <button
+            type="submit"
+            disabled={isLoading}
+            className="w-full py-3 bg-accent text-white rounded-lg font-medium hover:bg-accent/90 disabled:opacity-50 flex items-center justify-center gap-2"
+          >
+            {isLoading && <Loader2 className="animate-spin" size={18} />}
+            Sign in
+          </button>
+        </form>
+
+        <p className="text-center text-sm text-muted mt-6">
+          Don&apos;t have an account?{" "}
+          <Link href="/register" className="text-accent hover:underline">
+            Create one
+          </Link>
+        </p>
+      </div>
+    </div>
+  );
+}