fix: use gemini-2.0-flash (GA), 2.5-flash restricted for new API keys (#71)

Author: MatMatt

.github/scripts/helpers/gemini_client.py

@@ -30,9 +30,9 @@ def get_client() -> "genai.Client":
 
 
 # ---------------------------------------------------------------------------
-# Model & rate-limit constants  (Gemini 2.5 Flash – tier 1)
+# Model & rate-limit constants  (Gemini 2.0 Flash – tier 1)
 # ---------------------------------------------------------------------------
-MODEL_NAME = "gemini-2.5-flash-latest"
+MODEL_NAME = "gemini-2.0-flash"
 
 RPM_LIMIT = 995  # Requests per minute
 TPM_LIMIT = 750_000  # Tokens per minute