v3: fixes to database schema and user registration

src/pages/UserRegister.tsx

@@ -2,7 +2,7 @@ import { useEffect, useState } from "react";
 import type { SubmitEvent } from "react";
 import { Link, useNavigate, useSearchParams } from "react-router";
 
-import { API_URL } from "../config/api.ts";
+import { API_URL, VALIDATION } from "../config/api.ts";
 import { deserializeAuthResponse } from "../model.ts";
 import { useAuth } from "../hooks/useAuth.ts";
 import { PageShell } from "../components/PageShell.tsx";
@@ -109,14 +109,18 @@ export function UserRegister() {
             type="text"
             placeholder="Username"
             required
+            pattern={`[a-zA-Z0-9_]{${VALIDATION.USERNAME_MIN},${VALIDATION.USERNAME_MAX}}`}
+            title={`${VALIDATION.USERNAME_MIN}–${VALIDATION.USERNAME_MAX} characters: letters, numbers, or underscores`}
             disabled={formState.status === "submitting"}
             autoFocus
           />
           <input
             name="password"
             type="password"
-            placeholder="Password"
+            placeholder={`Password (min. ${VALIDATION.PASSWORD_MIN} characters)`}
             required
+            minLength={VALIDATION.PASSWORD_MIN}
+            maxLength={VALIDATION.PASSWORD_MAX}
             disabled={formState.status === "submitting"}
           />
           <button