Fix SMTP delivery, add password reset and user deletion

SMTP:
- Add connection/greeting/socket timeouts so a stalled Gmail
  connection no longer hangs sign-up
- Wrap sendMail in try/catch and fall back to logging the code
- Derive secure from port (465 implicit TLS vs 587 STARTTLS)
- Strip whitespace from the Gmail app password
- Document SMTP_HOST/SMTP_PORT in .env.example and environment.d.ts

Password reset (new):
- POST /(api)/auth/forgot-password emails a 6-digit code and does
  not reveal whether the address is registered
- POST /(api)/auth/reset-password validates the code, sets the new
  password, verifies the email, and signs the user in
- password_reset_codes table added to seed-db.mjs
- "Forgot password?" flow on the mobile sign-in screen

User deletion (new):
- DELETE /(api)/admin/users/[id], owner-only, blocks self-deletion
- Delete button with confirmation on the dashboard Users page

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

app/(api)/auth/forgot-password+api.ts

@@ -0,0 +1,61 @@
+import { createHash, randomInt } from "crypto";
+
+import { sql } from "@/lib/db";
+import { sendEmail } from "@/lib/mailer";
+
+const hashCode = (email: string, code: string): string =>
+  createHash("sha256").update(`${email}:${code}`).digest("hex");
+
+export async function POST(req: Request) {
+  const { email } = await req.json();
+
+  if (!email?.trim()) {
+    return Response.json({ error: "Email is required." }, { status: 400 });
+  }
+
+  const normalized = email.trim().toLowerCase();
+
+  try {
+    const users = await sql<{ id: string }>`
+      SELECT id FROM users WHERE email = ${normalized}
+    `;
+
+    // Don't reveal whether the address is registered: always answer the same.
+    if (!users[0]) {
+      return Response.json({ data: { sent: false } });
+    }
+
+    const code = String(randomInt(0, 1_000_000)).padStart(6, "0");
+
+    await sql`
+      INSERT INTO password_reset_codes (email, code_hash, expires_at)
+      VALUES (
+        ${normalized},
+        ${hashCode(normalized, code)},
+        CURRENT_TIMESTAMP + INTERVAL '15 minutes'
+      )
+      ON CONFLICT (email) DO UPDATE SET
+        code_hash = EXCLUDED.code_hash,
+        expires_at = EXCLUDED.expires_at,
+        attempts = 0
+    `;
+
+    const delivered = await sendEmail(
+      normalized,
+      "Reset your Waseel password",
+      `We received a request to reset your Waseel password.\n\nYour reset code is: ${code}\n\nIt expires in 15 minutes. If you didn't ask for this, you can ignore this email.`,
+    );
+
+    return Response.json({
+      data: {
+        sent: delivered,
+        // Without SMTP configured there is nothing to receive, so surface the
+        // code to keep the reset flow usable on a self-hosted box.
+        ...(delivered ? {} : { devCode: code }),
+      },
+    });
+  } catch (error) {
+    console.error("[FORGOT_PASSWORD]: ", error);
+    return Response.json({ error: "Internal Server Error" }, { status: 500 });
+  }
+}