fix: allow empty CRAWL_LIMIT env value

app/config.py

@@ -1,5 +1,5 @@
 from functools import lru_cache
-from pydantic import Field
+from pydantic import Field, field_validator
 from pydantic_settings import BaseSettings, SettingsConfigDict
 
 
@@ -19,6 +19,13 @@ class Settings(BaseSettings):
     session_secret: str = Field(default="dev-session-secret", min_length=8)
     mcp_token: str = "dev-mcp-token"
 
+    @field_validator("crawl_limit", mode="before")
+    @classmethod
+    def empty_crawl_limit_as_none(cls, value):
+        if value == "":
+            return None
+        return value
+
 
 @lru_cache
 def get_settings() -> Settings: