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.

examples/01-app-demos/hotdog/fly.toml

@@ -0,0 +1,26 @@
+# fly.toml app configuration file generated for hot-dog on 2024-12-19T18:23:45-08:00
+#
+# See https://fly.io/docs/reference/configuration/ for information about how to use this file.
+#
+
+app = 'hot-dog'
+primary_region = 'sjc'
+
+[build]
+
+[http_service]
+  internal_port = 8080
+  force_https = true
+  auto_stop_machines = 'stop'
+  auto_start_machines = true
+  min_machines_running = 0
+  processes = ['app']
+
+[[vm]]
+  memory = '1gb'
+  cpu_kind = 'shared'
+  cpus = 1
+
+[mounts]
+  source = "hotdogdb"
+  destination = "/usr/local/app/hotdogdb"