fix(queue): enforce sliced-model compatibility on cross-model dispatch (#2578)

A queue item's "Any <model>" button labeled itself from the file's slice
metadata while the scheduler used the row's target_model, so an X1C-sliced
item targeting H2D showed "Any X1C" above "assign to first idle H2D". The
mismatch itself was created silently: sliced-for metadata loads async, and
switching to model mode before it arrived pre-selected the alphabetically
first model (H2D on a mixed farm), after which the model dropdown hid
itself. Nothing validated compatibility, so the scheduler would hand X1C
G-code to an H2D.

Frontend: never default the target silently, keep the dropdown visible in
model mode (incompatible models disabled), label from the actual target,
warn on mismatch, block submit when incompatible.

Backend: new GCODE_COMPAT_FAMILIES table (X1/X1C/X1E/P1P/P1S interchange;
everything else exact-match; missing metadata never blocks). Queue create
and update reject incompatible targets with 400; the scheduler holds back
pre-existing mismatched rows with an actionable waiting_reason instead of
dispatching them.

backend/app/utils/printer_models.py

@@ -281,6 +281,41 @@ def get_rod_type(model: str | None) -> str | None:
     return None
 
 
+# G-code interchange families (#2578). A sliced 3MF may target a different
+# model ONLY within its family: same kinematics, build volume and G-code
+# dialect. X1/P1 series are the one proven-interchangeable group (256mm
+# CoreXY, single nozzle — mixed farms intentionally run X1-sliced jobs on
+# P1S/P1P). Everything else is exact-match only; extend deliberately, never
+# by assumption — a wrong entry here dispatches G-code onto hardware it was
+# not sliced for.
+# Short display names only (uppercase, no spaces) — is_gcode_compatible()
+# resolves internal codes (C11, O1D, ...) to short names before lookup.
+GCODE_COMPAT_FAMILIES = (frozenset(["X1", "X1C", "X1E", "P1P", "P1S"]),)
+
+
+def is_gcode_compatible(sliced_for_model: str | None, target_model: str | None) -> bool:
+    """Return True when G-code sliced for one model may be dispatched to the other.
+
+    Unknown/missing metadata on either side returns True — we can only
+    validate what the 3MF declares, and legacy files without
+    ``sliced_for_model`` must keep working.
+    """
+    if not sliced_for_model or not target_model:
+        return True
+
+    def _norm(model: str) -> str:
+        # Internal codes (e.g. "C11") → short names first, so "C11" vs "X1C"
+        # compares equal instead of leaning on family membership.
+        resolved = PRINTER_MODEL_ID_MAP.get(model.strip(), model)
+        return resolved.strip().upper().replace(" ", "").replace("-", "")
+
+    a = _norm(sliced_for_model)
+    b = _norm(target_model)
+    if a == b:
+        return True
+    return any(a in family and b in family for family in GCODE_COMPAT_FAMILIES)
+
+
 def normalize_printer_model_id(model_id: str | None) -> str | None:
     """Convert printer_model_id (internal code) to normalized short name.