feat(web): persist browser state

Keep settings, aliases, and recent drawings across browser sessions.

Load Start-page videos from a Pages-generated snapshot.

Cargo.toml

@@ -126,11 +126,20 @@ bincode = "1.3"
 # (Response) for the lazy per-script web font loader (#141).
 web-sys = { version = "0.3", features = [
     "Window",
+    "Storage",
+    "StorageManager",
     "Navigator",
     "Document",
     "Element",
     "HtmlAnchorElement",
     "Blob",
+    "File",
+    "FileSystemDirectoryHandle",
+    "FileSystemFileHandle",
+    "FileSystemGetDirectoryOptions",
+    "FileSystemGetFileOptions",
+    "FileSystemWritableFileStream",
+    "WritableStream",
     "Url",
     "Response",
     "Worker",