More fullstack fixes (#4737)

* allow `--server` only builds!

* rollback example

* capture `/:route` routes

* fix: properly implement file uploads in forms

* implement desktop form uploads

* Performant serialization of form bytes

* finish up file stuff

* cleanups

* add request headers to streaming context

* remove some unwraps

packages/web/Cargo.toml

@@ -85,7 +85,8 @@ features = [
     "File",
     "FileList",
     "FileReader",
-    "ReadableStream"
+    "ReadableStream",
+    "FormData"
 ]
 
 [build-dependencies]