feat: migrate to Cloudflare Workers with icon and version upload

Replace Express/SQLite and web/ with frontend/, worker/, and wrangler deploy. Add optional app icon upload, date-based app_version, and build-app workflow input.

Co-authored-by: Cursor <cursoragent@cursor.com>

worker/src/services/version.ts

@@ -0,0 +1,25 @@
+export class VersionValidationError extends Error {
+  constructor(message: string) {
+    super(message);
+    this.name = "VersionValidationError";
+  }
+}
+
+/** 当前日期版本，格式如 2026.5.29（月、日不补零） */
+export function getDefaultAppVersion(date = new Date()): string {
+  return `${date.getFullYear()}.${date.getMonth() + 1}.${date.getDate()}`;
+}
+
+export function validateAppVersion(input: string): string {
+  const value = input.trim() || getDefaultAppVersion();
+  if (!/^\d{4}\.\d{1,2}\.\d{1,2}$/.test(value)) {
+    throw new VersionValidationError(
+      "版本号格式应为 YYYY.M.D，例如 2026.5.29",
+    );
+  }
+  const [, month, day] = value.split(".").map(Number);
+  if (month < 1 || month > 12 || day < 1 || day > 31) {
+    throw new VersionValidationError("版本号中的月或日无效");
+  }
+  return value;
+}