Add ECO_MODE to PrimaryFiltrationMode enum (fixes #69) (#70)

SmartTub API returns ECO_MODE for primary filtration on some spas (e.g. J-375).
Missing enum value caused KeyError when fetching full spa status after login.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: mdz

smarttub/api.py

@@ -437,7 +437,7 @@ def __init__(self, spa: Spa, **properties):
 
 
 class SpaPrimaryFiltrationCycle(SpaState):
-    PrimaryFiltrationMode = Enum("PrimaryFiltrationMode", "NORMAL NANO_MODE")
+    PrimaryFiltrationMode = Enum("PrimaryFiltrationMode", "NORMAL NANO_MODE ECO_MODE")
 
     def __init__(self, spa: Spa, **properties):
         self.spa = spa