Fix gin-config ambiguity: pin module name, remove redundant import

- Use gin.configurable(module=...) to prevent __main__ vs module name clash
- Remove `import src.training.train_gtauav` from gin files (already loaded)
- Use short selector names (TrainConfigGTAUAV) in all gin configs

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/training/train_gtauav.py

@@ -55,7 +55,7 @@ _DINO_SAT = "nn_models/DINO_SAT/model.safetensors"
 _LRSCLIP = "nn_models/LRSCLIP/DGTRS-CLIP-ViT-L-14.pt"
 
 
-@gin.configurable
+@gin.configurable(module="src.training.train_gtauav")
 @dataclass
 class TrainConfigGTAUAV:
     """Training configuration for GTA-UAV experiment."""