fix(claude_sdk,conversations,rotation): context size from the last api call, new-day text by rotation reason

src/beaver_gateway/storage/models.py

@@ -299,6 +299,8 @@ class Usage(SQLModel, table=True):
     output_tokens: int = 0
     cache_read_tokens: int = 0
     cache_creation_tokens: int = 0
+    context_tokens: int | None = Field(default=None)
+    """Input of the turn's last API call - the real context size."""
     cost_usd: float | None = Field(default=None)
     duration_ms: int | None = Field(default=None)
     num_turns: int | None = Field(default=None)