Enhance GPU flavor scanning and update documentation

- Introduced SCAN_POOLS configuration to specify pools for GPU flavor scanning.
- Updated the `flavors` command to scan specified pools and list available GPU flavors based on `FLAVOR_PREFERENCE`.
- Revised CLI documentation to reflect changes in the `flavors` command behavior.
- Enhanced decision documentation to include details about GPU pool scanning.
- Updated setup instructions to guide users on selecting appropriate GPU pools.

src/gpu_rent/config.py

@@ -80,6 +80,7 @@ class Config:
     default_flavor_id: str
     flavor_preference: tuple[str, ...]
     flavor_fallback: bool
+    scan_pools: str
     default_spot: bool
     keep_floating_ip: bool
     idle_minutes: int
@@ -185,6 +186,7 @@ def load_config(*, require_auth: bool = True) -> Config:
             ("4090-24", "4090-48", "a5000", "a100-40"),
         ),
         flavor_fallback=_as_bool(os.environ.get("FLAVOR_FALLBACK"), True),
+        scan_pools=(os.environ.get("SCAN_POOLS") or "ru-6,ru-7").strip(),
         default_spot=_as_bool(os.environ.get("DEFAULT_SPOT"), True),
         keep_floating_ip=_as_bool(os.environ.get("KEEP_FLOATING_IP"), False),
         idle_minutes=_as_int(os.environ.get("IDLE_MINUTES"), 30),