feat(sponsors): drop the sidebar slot and simplify the Sponsors page

The sidebar no longer carries a sponsor card. The backend stops serving
the "sidebar" slot, so a sponsors.json entry that still lists it keeps
only its other slots and one listing nothing else is dropped. Its
rotation, three-sponsor cap and collapsed-rail logo rendering go with it.

The Sponsors page now lists only real sponsors: the "Your brand here"
card shows only as the empty state instead of sitting in the grid and
repeating the header's Become a sponsor button, and the Available
placements section and its slot-occupancy helper are removed. Cards are
larger, two per row on wide screens. Unused i18n keys are dropped from
every locale.

frontend/src/components/sponsor/SponsorCard.css

@@ -184,28 +184,37 @@
 .sponsor-card-card .sponsor-main {
   flex-direction: column;
   align-items: flex-start;
-  padding: 16px;
+  gap: 16px;
+  padding: 24px;
 }
 
 .sponsor-card-card .sponsor-logo {
-  width: 56px;
-  height: 56px;
+  width: 72px;
+  height: 72px;
+  border-radius: 12px;
+}
+
+.sponsor-card-card .sponsor-logo-fallback {
+  font-size: 28px;
+}
+
+.sponsor-card-card .sponsor-body {
+  gap: 6px;
+}
+
+.sponsor-card-card .sponsor-title {
+  font-size: 17px;
+  line-height: 1.4;
+}
+
+.sponsor-card-card .sponsor-text {
+  font-size: 14px;
+  line-height: 1.6;
 }
 
 .sponsor-card-card .sponsor-visit {
   margin-top: auto;
-}
-
-.sponsor-card-icon {
-  justify-content: center;
-  padding: 6px;
-  border-color: transparent;
-  background: transparent;
-}
-
-.sponsor-card-icon .sponsor-logo {
-  width: 32px;
-  height: 32px;
+  font-size: 14px;
 }
 
 @media (max-width: 576px) {

frontend/src/components/sponsor/SponsorCard.stories.tsx

@@ -7,7 +7,7 @@ import SponsorCard from './SponsorCard';
 const sponsor: Sponsor = {
   id: 'acme-2026-10',
   name: 'Acme VPS',
-  slots: ['dashboard', 'sidebar', 'page', 'login'],
+  slots: ['dashboard', 'page', 'login'],
   until: '2099-01-01T00:00:00Z',
   title: { en: 'Acme VPS — fast NVMe servers', fa: 'سرورهای سریع Acme' },
   text: { en: 'Deploy 3X-UI in 60 seconds. 20% off for panel users.' },
@@ -57,9 +57,8 @@ const meta = {
   argTypes: {
     sponsor: { description: 'Sponsor entry from GET /sponsors.' },
     variant: {
-      description: 'banner (dashboard), compact (sidebar/login) or card (Sponsors page).',
+      description: 'banner (dashboard), compact (login) or card (Sponsors page).',
     },
-    iconOnly: { description: 'Logo-only rendering for the collapsed sidebar rail.' },
     onClose: { description: 'When set, shows a close button (temporary dismiss).' },
   },
   args: { sponsor },
@@ -81,7 +80,7 @@ export const Banner: Story = {
 export const Compact: Story = {
   args: { variant: 'compact', onClose: () => {} },
   render: (args) => (
-    <div style={{ width: 204 }}>
+    <div style={{ width: 334 }}>
       <SponsorCard {...args} />
     </div>
   ),
@@ -108,23 +107,6 @@ export const BannerLongCopy: Story = {
   },
 };
 
-export const SidebarLongCopy: Story = {
-  args: { variant: 'compact', sponsor: longSponsor, onClose: () => {} },
-  render: (args) => (
-    <div style={{ width: 204 }}>
-      <SponsorCard {...args} />
-    </div>
-  ),
-  play: async ({ canvasElement }) => {
-    await expectNotClipped(canvasElement, '.sponsor-title');
-    await expectInsideCard(canvasElement, '.sponsor-text');
-    await expect(part(canvasElement, '.sponsor-main')).toHaveAttribute(
-      'title',
-      `${longSponsor.title.en}\n${longSponsor.text.en}`,
-    );
-  },
-};
-
 export const LoginLongCopy: Story = {
   args: { variant: 'compact', sponsor: longSponsor, onClose: () => {} },
   render: (args) => (
@@ -135,6 +117,10 @@ export const LoginLongCopy: Story = {
   play: async ({ canvasElement }) => {
     await expectNotClipped(canvasElement, '.sponsor-title');
     await expectNotClipped(canvasElement, '.sponsor-text');
+    await expect(part(canvasElement, '.sponsor-main')).toHaveAttribute(
+      'title',
+      `${longSponsor.title.en}\n${longSponsor.text.en}`,
+    );
   },
 };
 
@@ -151,7 +137,3 @@ export const PageLongCopy: Story = {
     await expectNotClipped(canvasElement, '.sponsor-title');
   },
 };
-
-export const IconOnly: Story = {
-  args: { iconOnly: true },
-};

frontend/src/components/sponsor/SponsorCard.tsx

@@ -12,7 +12,6 @@ export type SponsorCardVariant = 'banner' | 'compact' | 'card';
 export interface SponsorCardProps {
   sponsor: Sponsor;
   variant?: SponsorCardVariant;
-  iconOnly?: boolean;
   onClose?: () => void;
 }
 
@@ -36,33 +35,13 @@ function SponsorLogo({ sponsor }: { sponsor: Sponsor }) {
   );
 }
 
-export default function SponsorCard({
-  sponsor,
-  variant = 'banner',
-  iconOnly = false,
-  onClose,
-}: SponsorCardProps) {
+export default function SponsorCard({ sponsor, variant = 'banner', onClose }: SponsorCardProps) {
   const { t, i18n } = useTranslation();
   const lang = i18n.resolvedLanguage || i18n.language || 'en';
   const title = pickLocale(sponsor.title, lang) || sponsor.name;
   const text = pickLocale(sponsor.text, lang);
   const tag = t('pages.sponsors.tag');
 
-  if (iconOnly) {
-    return (
-      <a
-        className="sponsor-card sponsor-card-icon"
-        href={sponsor.link}
-        target="_blank"
-        rel="noopener noreferrer sponsored"
-        title={`${tag} · ${title}`}
-        aria-label={`${tag}: ${title}`}
-      >
-        <SponsorLogo sponsor={sponsor} />
-      </a>
-    );
-  }
-
   return (
     <div className={`sponsor-card sponsor-card-${variant}`}>
       <a

frontend/src/components/sponsor/SponsorSlot.tsx

@@ -1,4 +1,4 @@
-import { useEffect, useState } from 'react';
+import { useState } from 'react';
 
 import { useSponsorsQuery } from '@/api/queries/useSponsorsQuery';
 import {
@@ -9,47 +9,29 @@ import {
 } from '@/lib/sponsors';
 import SponsorCard, { type SponsorCardVariant } from './SponsorCard';
 
-const ROTATE_MS = 30_000;
-
 interface SponsorSlotProps {
   slot: Slot;
   variant?: SponsorCardVariant;
-  iconOnly?: boolean;
-  rotate?: boolean;
   className?: string;
 }
 
-export default function SponsorSlot({
-  slot,
-  variant = 'banner',
-  iconOnly,
-  rotate,
-  className,
-}: SponsorSlotProps) {
+export default function SponsorSlot({ slot, variant = 'banner', className }: SponsorSlotProps) {
   const { data } = useSponsorsQuery();
   const [, setDismissTick] = useState(0);
-  const [index, setIndex] = useState(0);
 
   // Re-filtered each render so a close (dismissTick bump) re-reads localStorage.
   const visible = sponsorsForSlot(data.sponsors, slot).filter(
     (s) => !isSponsorDismissed(s.id, slot),
   );
 
-  useEffect(() => {
-    if (!rotate || visible.length < 2) return;
-    const timer = window.setInterval(() => setIndex((i) => i + 1), ROTATE_MS);
-    return () => window.clearInterval(timer);
-  }, [rotate, visible.length]);
-
   if (visible.length === 0) return null;
-  const sponsor = visible[(rotate ? index : 0) % visible.length];
+  const sponsor = visible[0];
 
   return (
     <div className={className}>
       <SponsorCard
         sponsor={sponsor}
         variant={variant}
-        iconOnly={iconOnly}
         onClose={() => {
           dismissSponsor(sponsor.id, slot);
           setDismissTick((n) => n + 1);