DRY pass #2, batch 5, F14: the web's repeated class lists become component classes (#5372)

style.css gains the classes the views spelled out in full: .section-label
(17 sites), .hint (20), .form-error (13), .alert-error (5), .row-card (5),
.list-empty (5), .field (5), .page-shell (3), and the small row action
.btn-sm (4) / .btn-sm-danger (3). Only exact runs moved, so nothing renders
differently; spacing a site adds beyond a run stays a utility beside it.

Kept: the Reminders and Timeline small buttons. They carry no text colour
and inherit it, so putting them on .btn-sm would recolour them.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/components/InviteList.vue

@@ -109,7 +109,7 @@ onMounted(() => {
 
 <template>
   <section class="flex flex-col gap-5">
-    <h2 class="text-xs font-semibold uppercase tracking-wide text-neutral-400">Invites</h2>
+    <h2 class="section-label">Invites</h2>
 
     <OneTimeLink
       v-if="freshLink"
@@ -132,7 +132,7 @@ onMounted(() => {
         <select
           id="invite-days"
           v-model.number="days"
-          class="rounded-lg border border-neutral-300 bg-white px-3 py-2 text-sm text-neutral-900 shadow-sm focus:outline-none focus-visible:ring-2 focus-visible:ring-brand dark:border-neutral-700 dark:bg-neutral-800 dark:text-neutral-100"
+          class="field"
         >
           <option v-for="l in LIFETIMES" :key="l.days" :value="l.days">{{ l.label }}</option>
         </select>
@@ -140,15 +140,15 @@ onMounted(() => {
       <BaseButton type="submit" :loading="creating">Create invite</BaseButton>
     </form>
 
-    <p v-if="error" class="text-sm text-red-600 dark:text-red-400">{{ error }}</p>
+    <p v-if="error" class="form-error">{{ error }}</p>
 
-    <div v-if="loading" class="py-6 text-center text-sm text-neutral-400">Loading…</div>
+    <div v-if="loading" class="list-empty">Loading…</div>
     <p v-else-if="!invites.length" class="text-sm text-neutral-400">No invites yet.</p>
     <ul v-else class="flex flex-col gap-2">
       <li
         v-for="i in invites"
         :key="i.id"
-        class="flex items-center justify-between gap-4 rounded-xl border border-neutral-200 px-4 py-3 dark:border-neutral-800"
+        class="row-card"
       >
         <div class="min-w-0">
           <p class="truncate text-sm font-medium text-neutral-800 dark:text-neutral-100">
@@ -159,7 +159,7 @@ onMounted(() => {
         <button
           v-if="i.status === 'pending'"
           type="button"
-          class="shrink-0 rounded-md border border-neutral-300 px-2.5 py-1 text-xs text-red-600 hover:bg-red-50 focus:outline-none focus-visible:ring-2 focus-visible:ring-brand dark:border-neutral-700 dark:text-red-400 dark:hover:bg-red-950/40"
+          class="shrink-0 btn-sm-danger"
           @click="revoke(i)"
         >
           Revoke