feat(nam): download 10 new A2 models for bass, orange, and other missing categories

Bank 7 — Bass: Ampeg PF20T, Aguilar Tone Hammer 500, GK 800RB (Gallien-Krueger), Aguilar DB751
Bank 7 — Orange: Orange Rocker 30 Dirty + Natural
Bank 7 — Others: Fender Bassman dimed, Hiwatt DR103 Bright + Cornish, Supro Black Magick M3

All SlimmableContainer v0.7.0, ~287-295 KB, verified JSON.
Also fixed Bank 2 Tone3000 storage keys to include .nam extension (Tone3000 changed URL format).
Inventory updated: 54 → 64 total models.

src/presets/types.py

@@ -82,6 +82,7 @@ class FXBlock:
     enabled: bool = True
     bypass: bool = False
     params: dict[str, float] = field(default_factory=dict)
+    subtype: str = ""               # Algorithm variant (e.g. "hall"/"spring"/"plate" for reverb)
     nam_model_path: str = ""        # Path to .nam file (for NAM_AMP type)
     ir_file_path: str = ""          # Path to .wav IR file (for IR_CAB type)