fix: Redis expire guard, transferOwnership prev-owner, SVG regex

- Redis get() rejects legacy expire=0 entries and cleans them up
- transferOwnership invalidates previous owner in addition to new
- SVG regex uses non-greedy match and handles self-closing <svg />
- SVG fallback returns empty string instead of HTML wrapper
- Memory channel comment: FIFO eviction, not timestamp-based

apps/nextjs/src/app/api/user-medias/svg-purify.ts

@@ -86,8 +86,8 @@ export const sanitizeSvg = (svgText: string) => {
   // linkedom's DOMParser omits html/body for fragment-only SVG; DOMPurify needs a body root.
   const wrapped = `<html><body>${svgText}</body></html>`;
   const sanitized = purify.sanitize(wrapped, svgSanitizeOptions);
-  const svgMatch = sanitized.match(/<svg[\s\S]*<\/svg>/i);
-  return svgMatch ? svgMatch[0] : sanitized;
+  const svgMatch = sanitized.match(/<svg[\s\S]*?(?:<\/svg>|\/>)/i);
+  return svgMatch ? svgMatch[0] : "";
 };
 
 export { svgSanitizeOptions, purify };