Add option to limit squadron sizes and begin full.

Adding temporarily as an option to make sure it's not a terrible idea,
but the old mode will probably go away.

Fixes https://github.com/dcs-liberation/dcs_liberation/issues/1583.
Fixes https://github.com/dcs-liberation/dcs_liberation/issues/2808.

game/settings/settings.py

@@ -245,6 +245,15 @@ class Settings:
             "this many pilots each turn up to the limit."
         ),
     )
+    # Feature flag for squadron limits.
+    enable_squadron_aircraft_limits: bool = boolean_option(
+        "Enable per-squadron aircraft limits",
+        CAMPAIGN_MANAGEMENT_PAGE,
+        PILOTS_AND_SQUADRONS_SECTION,
+        default=False,
+        remember_player_choice=True,
+        detail="If set, squadrons will be limited to a maximum number of aircraft.",
+    )
 
     # HQ Automation
     automate_runway_repair: bool = boolean_option(