feat(gui): per-filament nozzle volume selection and persistence

- FilamentMapDialog's manual page understands volume types: a mixed
  (Hybrid) extruder shows separate Standard / High Flow drop zones
  with live sub-nozzle counts, a validation timer with an inline
  error + "set nozzle count" suggestion, and composes a per-filament
  volume map on OK (persisted to the plate or globally)
- switching an extruder's Flow type rewrites the affected plate map
  entries; plate maps stay sized across filament add/delete/count
  changes (values keep their filament, no index shift)
- CLI: manual mapping on multi-nozzle printers synthesizes the volume
  map from extruder flow types when absent; nozzle-manual mode
  requires explicit maps; computed maps land on the plate so exported
  projects carry filament_volume_maps
- filament_nozzle_map joins the project options (selection seeding +
  filament-count resizing)
- pot entries for the new dialog strings

All 19 reference fixtures byte-identical; slicing an exported Hybrid
project reproduces its g-code byte-for-byte with the volume map
round-tripped through model_settings.config.

src/slic3r/GUI/Plater.hpp

@@ -586,7 +586,9 @@ public:
 
     void set_global_filament_map_mode(FilamentMapMode mode);
     void set_global_filament_map(const std::vector<int>& filament_map);
+    void set_global_filament_volume_map(const std::vector<int>& filament_volume_map);
     std::vector<int> get_global_filament_map() const;
+    std::vector<int> get_global_filament_volume_map() const;
     FilamentMapMode get_global_filament_map_mode() const;
 
     void update_menus();
@@ -748,6 +750,11 @@ public:
 
     void update_machine_sync_status();
 
+    // Rewrite every plate's per-filament volume choice for the filaments grouped onto this
+    // extruder after its Flow type changed (Hybrid resets them to Standard so the user
+    // re-assigns concrete volumes in the grouping dialog).
+    void update_filament_volume_map(int extruder_id, int volume_type);
+
 #if ENABLE_ENVIRONMENT_MAP
     void init_environment_texture();
     unsigned int get_environment_texture_id() const;