outrank Arco button variants and drop the credential hint

The neon tube rules never applied. Arco emits .arco-btn-primary along
with three attribute variants ([type='button'], [type='submit'],
[type='reset']) that lift specificity to (0,2,0), and their :hover forms
reach (0,3,0) — all of which beat a bare .arco-btn-primary. Every rule
now uses .arco-btn.arco-btn-X[type='...'] so the skin wins regardless of
the rendered html-type; login is a submit button, which is why it stayed
solid.

Verified with jsdom computed styles against the real arco.css.

Also remove the default-credential chips from the login page: printing
admin / 123456 on a sign-in screen leaks the credentials of a reachable
deployment. The one-click fill shortcut stays. The test that asserted
the hint is now shown is inverted to assert it is absent.

packages/client/src/views/LoginView.vue

@@ -169,13 +169,8 @@ function fillDefaultCredentials() {
       </form>
 
       <footer class="login-ft">
-        <div class="login-sep"><span>{{ t("login.defaultCredentialsHint") }}</span></div>
-        <div class="login-chips">
-          <span class="login-chip"><span class="dot"></span>{{ t("login.username") }} <b>admin</b></span>
-          <span class="login-chip"><span class="dot"></span>{{ t("login.passwordPlaceholder") }} <b>123456</b></span>
-        </div>
         <button type="button" class="login-copy" @click="fillDefaultCredentials">
-          ⧉ {{ t("login.fillDefaultCredentials") }}
+          ⧉ {{ t("login.fillDefaults") }}
         </button>
         <p class="login-legal">
           {{ t("login.localDeploymentNote") }}<br />
@@ -499,58 +494,6 @@ function fillDefaultCredentials() {
   text-align: center;
 }
 
-.login-sep {
-  display: flex;
-  align-items: center;
-  gap: 11px;
-  margin: 0 0 14px;
-  font-size: 11px;
-  color: var(--text-faint);
-
-  &::before,
-  &::after {
-    content: "";
-    flex: 1;
-    height: 1px;
-    background: var(--border-light);
-  }
-}
-
-.login-chips {
-  display: flex;
-  flex-wrap: wrap;
-  justify-content: center;
-  gap: 7px;
-  margin-bottom: 14px;
-}
-
-.login-chip {
-  display: inline-flex;
-  align-items: center;
-  gap: 6px;
-  padding: 4px 9px;
-  border: 1px solid var(--border-light);
-  border-radius: 20px;
-  background: $bg-card;
-  font-family: $font-code;
-  font-size: 11px;
-  line-height: 1.4;
-  color: $text-muted;
-
-  b {
-    color: $accent-primary;
-    font-weight: 600;
-  }
-
-  .dot {
-    width: 5px;
-    height: 5px;
-    border-radius: 50%;
-    background: $success;
-    box-shadow: 0 0 5px $success;
-  }
-}
-
 .login-copy {
   width: 100%;
   height: 34px;