Hardcode build number in backend

backend/app/config.py

@@ -2,6 +2,7 @@ from typing import Optional
 from pydantic import AliasChoices, Field
 from pydantic_settings import BaseSettings, SettingsConfigDict
 
+from .build_info import BUILD_NUMBER
 
 class Settings(BaseSettings):
     model_config = SettingsConfigDict(env_prefix="")
@@ -38,9 +39,7 @@ class Settings(BaseSettings):
     artwork_cache_mode: str = Field(
         default="remote", validation_alias=AliasChoices("ARTWORK_CACHE_MODE")
     )
-    site_build_number: Optional[str] = Field(
-        default=None, validation_alias=AliasChoices("SITE_BUILD_NUMBER")
-    )
+    site_build_number: Optional[str] = Field(default=BUILD_NUMBER)
     site_banner_enabled: bool = Field(
         default=False, validation_alias=AliasChoices("SITE_BANNER_ENABLED")
     )