feat: layout url import

feat: backup import (except chords)
feat: legacy layout import
feat: separate layout, chord & setting backup downloads

src/lib/serialization/actions.ts

@@ -24,7 +24,7 @@ export function decompressActions(raw: Uint8Array): number[] {
   const actions: number[] = []
   for (let i = 0; i < raw.length; i++) {
     let action = raw[i]
-    if (action < 32) {
+    if (action > 0 && action < 32) {
       action = (action << 8) | raw[++i]
     }
     actions.push(action)

src/lib/serialization/base64.ts

@@ -20,7 +20,7 @@ export async function toBase64(blob: Blob): Promise<string> {
   })
 }
 
-export async function fromBase64(base64: string): Promise<Blob> {
+export async function fromBase64(base64: string, fetch = window.fetch): Promise<Blob> {
   return fetch(
     `data:application/octet-stream;base64,${base64
       .replaceAll(".", "+")