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/reset-password+api.ts

@@ -0,0 +1,79 @@
+import { createHash } from "crypto";
+
+import { sql } from "@/lib/db";
+import { hashPassword } from "@/lib/password";
+import { issueSession, toProfile } from "@/lib/users";
+
+const hashCode = (email: string, code: string): string =>
+  createHash("sha256").update(`${email}:${code}`).digest("hex");
+
+export async function POST(req: Request) {
+  const { email, code, password } = await req.json();
+
+  if (!email?.trim() || !/^\d{6}$/.test(code ?? "")) {
+    return Response.json(
+      { error: "Email and a 6-digit code are required." },
+      { status: 400 },
+    );
+  }
+
+  if (typeof password !== "string" || password.length < 8) {
+    return Response.json(
+      { error: "Password must be at least 8 characters." },
+      { status: 400 },
+    );
+  }
+
+  const normalized = email.trim().toLowerCase();
+
+  try {
+    const valid = await sql<{ email: string }>`
+      SELECT email FROM password_reset_codes
+      WHERE email = ${normalized}
+        AND code_hash = ${hashCode(normalized, code)}
+        AND expires_at > CURRENT_TIMESTAMP
+    `;
+
+    if (!valid[0]) {
+      await sql`
+        UPDATE password_reset_codes SET attempts = attempts + 1
+        WHERE email = ${normalized}
+      `;
+
+      return Response.json(
+        { error: "Invalid or expired reset code." },
+        { status: 400 },
+      );
+    }
+
+    // A successful reset also proves control of the mailbox, so verify it too.
+    const rows = await sql<{
+      id: string;
+      name: string;
+      email: string;
+      role: string | null;
+    }>`
+      UPDATE users
+      SET password_hash = ${hashPassword(password)}, email_verified = TRUE
+      WHERE email = ${normalized}
+      RETURNING id, name, email, role
+    `;
+
+    const user = rows[0];
+
+    if (!user) {
+      return Response.json({ error: "User not found." }, { status: 404 });
+    }
+
+    await sql`DELETE FROM password_reset_codes WHERE email = ${normalized}`;
+
+    const session = issueSession(user);
+
+    return Response.json({
+      data: { token: session.token, user: toProfile(user) },
+    });
+  } catch (error) {
+    console.error("[RESET_PASSWORD]: ", error);
+    return Response.json({ error: "Internal Server Error" }, { status: 500 });
+  }
+}