Name the sizes a node can ask for

Raw cpus and gpus are a property of the machines an installation has, so a node
written against a cluster quietly stops meaning anything when the cluster is
replaced. A node says "gpu-small" instead, and what that is stored here —
editable, and read again every time the node is built, so changing the flavor
changes what the next run gets.

Memory joins the schema properly (`ram`, in MB, accepting "2G"), along with
`duration_s` for how long a node is expected to take. That one is recorded and
shown and nothing else yet: a statement for whoever is planning around the node,
not a limit — the limit is still `timeout`.

A flavor and a number for the same thing is refused, compared by value so an
editor writing the whole object back with its defaults still round-trips. A name
nothing stores is refused at the save, which covers the canvas and `fluksio
sync` at once, and deleting one a node still asks for says which node.

Four sizes are seeded on an installation that has none, and never re-seeded:
re-adding one somebody deliberately removed is an argument nobody wins.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01A6HeySA27EkGANZN95QySW

backend/fluksio/sdk/client.py

@@ -272,6 +272,16 @@ class Client:
         result = self._call("GET", "/flows/")
         return list(result.get("data") or [])
 
+    def flavors(self) -> list[dict[str, Any]]:
+        """The named sizes a node can ask for."""
+        result = self._call("GET", "/flavors/")
+        return list(result.get("data") or [])
+
+    def resources(self) -> dict[str, Any]:
+        """Every machine, what is free of it, and which nodes are queued."""
+        result: dict[str, Any] = self._call("GET", "/workers/resources")
+        return result
+
     # -- how the engine is doing -------------------------------------------
 
     def summary(self) -> dict[str, Any]: