codify "platform" into resolution logic, server-fn/fullstack overhaul (#4596)

overhaul dioxus fullstack using a new implementation of server_fn

This PR is a complete rewrite of dioxus fullstack designed to improve compatibility with axum and to fix a number of compilation errors based on feature flag unification plumbing through macros.

packages/core/Cargo.toml

@@ -25,6 +25,7 @@ warnings = { workspace = true }
 futures-util = { workspace = true, default-features = false, features = ["alloc", "std"] }
 serde = { workspace = true, optional = true, features = ["derive"] }
 subsecond = { workspace = true }
+anyhow = { workspace = true }
 
 [dev-dependencies]
 dioxus = { workspace = true }