fix(revenue): match reference poster modal UI 1:1

The 推广海报 modal on the revenue page used a bespoke .uc-modal card —
white panel, 12px radius, heavy shadow, title bar, corner × button and a
full-width 保存海报 button — plus a light-gray plate with its own
border-radius around the poster canvas. None of that exists in the
reference theme, so the popup read as bordered and off-spec.

Rebuild the modal on the reference poster-share structure: a borderless
360px .modal-dialog.poster-share centred by .modal.flex.jc, a
.loading-mask overlay while the canvas renders, and the download/close
buttons moved onto a .abs-center.hover-show-con layer that only fades in
on hover. initAffiliatePoster() now drives Bootstrap 3 modal semantics
(.in toggle, .modal-backdrop, body.modal-open, ESC and backdrop-click to
close), mirroring the existing openChargeModal/closeChargeModal pair, and
animates .modal-content from the 220px placeholder to the poster's real
height before clearing the inline styles.

No CSS added — every rule the reference modal needs was already ported.
Drop the now-dead .uc-affiliate-poster rules; the shared .uc-modal shell
and openModal/closeModal stay for the withdraw and transfer modals.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

assets/css/routes/user-center/revenue-earnings.css

@@ -214,9 +214,3 @@
   .uc-content .uc-revenue-summary-row--explain { grid-template-columns: 1fr; }
   .uc-content .uc-revenue-summary-row--explain .uc-reward-richtext { grid-column: 1; }
 }
-
-/* 推广海报预览弹窗：舞台居中，canvas 自适应弹窗宽度。 */
-.uc-content .uc-affiliate-poster { display: grid; place-items: center; min-height: 120px; }
-.uc-content .uc-affiliate-poster img,
-.uc-content .uc-affiliate-poster canvas { display: block; max-width: 100%; height: auto; margin: 0 auto; border-radius: 12px; background: var(--surface-2, #f7f8fa); }
-.uc-content .uc-affiliate-poster p { margin: 0; text-align: center; }