feat: 媒体库 blob 去重存储与品牌/注册等前端调整

新增：
- blob_store 二进制去重存储 + blob_dedup 测试

其它：
- 后端 settings/auth/media_library/upload/operations 服务与 handler 调整
- 前端品牌（BrandLockup/BrandCropModal/BrandSeoPanel）、注册、媒体库、分析详情页、Header/SiteChrome 等更新

frontend/lib/brand.ts

@@ -28,8 +28,8 @@ export type BrandSlot = "logo_light" | "logo_dark" | "favicon";
 /** 页眉品牌形式 */
 export type BrandMark = "image_text" | "image" | "text";
 
-/** 图槽画幅。方标是默认；其余是页眉里常见的横版比例 */
-export type BrandLogoSize = "sq" | "2x1" | "3x1" | "4x1" | "16x9";
+/** 图槽画幅。方标是默认；其余是页眉里常见的横版比例；auto=原图比例自适应宽度 */
+export type BrandLogoSize = "sq" | "2x1" | "3x1" | "4x1" | "16x9" | "auto";
 
 export const BRAND_LOGO_SIZES: { id: BrandLogoSize; label: string; w: number; h: number }[] = [
   { id: "sq", label: "方标", w: 36, h: 36 },
@@ -37,6 +37,7 @@ export const BRAND_LOGO_SIZES: { id: BrandLogoSize; label: string; w: number; h:
   { id: "3x1", label: "3:1", w: 120, h: 40 },
   { id: "4x1", label: "4:1", w: 176, h: 44 },
   { id: "16x9", label: "16:9", w: 96, h: 54 },
+  { id: "auto", label: "原图", w: 0, h: 40 },
 ];
 
 export function normalizeBrandMark(raw: unknown): BrandMark {
@@ -47,10 +48,38 @@ export function normalizeBrandMark(raw: unknown): BrandMark {
 
 export function normalizeBrandLogoSize(raw: unknown): BrandLogoSize {
   const s = String(raw ?? "").trim();
-  if (s === "sq" || s === "2x1" || s === "3x1" || s === "4x1" || s === "16x9") return s;
+  if (s === "sq" || s === "2x1" || s === "3x1" || s === "4x1" || s === "16x9" || s === "auto") return s;
   return "sq";
 }
 
+/** 各固定画幅的宽高比（auto 不在此表，代表自由比例） */
+export const BRAND_LOGO_SIZE_ASPECT: Partial<Record<BrandLogoSize, number>> = {
+  sq: 1,
+  "2x1": 2,
+  "3x1": 3,
+  "4x1": 4,
+  "16x9": 16 / 9,
+};
+
+/**
+ * 根据图片原始比例推荐画幅：
+ * 与某个固定画幅差距 ≤15% 时推荐该画幅，否则推荐 auto（原图自适应）。
+ */
+export function suggestLogoSize(naturalW: number, naturalH: number): BrandLogoSize {
+  if (!naturalW || !naturalH) return "auto";
+  const ratio = naturalW / naturalH;
+  let best: BrandLogoSize = "sq";
+  let bestDelta = Infinity;
+  for (const [id, a] of Object.entries(BRAND_LOGO_SIZE_ASPECT) as [BrandLogoSize, number][]) {
+    const delta = Math.abs(ratio - a) / a;
+    if (delta < bestDelta) {
+      bestDelta = delta;
+      best = id;
+    }
+  }
+  return bestDelta <= 0.15 ? best : "auto";
+}
+
 export function brandLogoBox(size: BrandLogoSize): { w: number; h: number } {
   const found = BRAND_LOGO_SIZES.find((item) => item.id === size);
   return found ? { w: found.w, h: found.h } : { w: 36, h: 36 };
@@ -72,6 +101,13 @@ export function normalizeBrandLogoFit(raw: unknown): BrandLogoFit {
   return "contain";
 }
 
+/** 标语是否在页眉显示；缺省 true（与后端缺省一致） */
+export function normalizeBrandSloganVisible(raw: unknown): boolean {
+  if (typeof raw === "boolean") return raw;
+  if (typeof raw === "string") return raw.trim().toLowerCase() !== "false";
+  return true;
+}
+
 export const BRAND_LIMITS = {
   wordmark: 16,
   slogan: 32,