feat: report indexing progress with page counts in status panel

backend/app/models.py

@@ -38,6 +38,9 @@ class StatusResponse(BaseModel):
     model: str = ""
     last_indexed_at: str | None = None
     errors: list[str] = Field(default_factory=list)
+    pages_processed: int = 0
+    pages_total: int = 0
+    current_file: str | None = None
 
 
 class HealthResponse(BaseModel):