Emit clipped `<image href>` for fills with a registered media URL instead
of Skia base64 embeds. Register URLs from the frontend and exporter via
store_image_url. Cover rect, path, frame, and text (glyph clip) cases in
SVG export tests.
Closes#11383
* ✨ Add export job model, store and scheduler to exporter
* ✨ Render wasm exports on pooled worker threads
* ✨ Add export job REST API to exporter
* ✨ Use export job API and allow cancelling wasm exports
* 🔧 Show export jobs in the internal debug panel
* 🔧 Pass flags and export job settings to the exporter container
* 📚 Document the exporter job API and its redis layout
* ✨ Add headless wasm render backend to the exporter
* ♻️ Move render-wasm bridge to common and split wasm builds
* 🔧 Upload builtin font variants in the wasm exporter
* ♻️ Move shared font and resources utils out of render_wasm
* ⚡ Fetch only the exported roots in the wasm exporter
* ⚡ Bound save_layer rects in the vector export path
