feat: Organize public uploads into daily directories based on timezone

Co-authored-by: aider (gemini/gemini-2.5-pro) <aider@aider.chat>

app/config.py

@@ -24,6 +24,7 @@ class Settings:
     log_level: str = "INFO"
     chunked_uploads_enabled: bool = False
     chunk_size_mb: int = 95
+    timezone: str = "UTC"
 
 def _hash_password(pw: str) -> str:
     """Return PBKDF2-SHA256 hash of a password."""
@@ -71,6 +72,7 @@ def load_settings() -> Settings:
         chunk_size_mb = int(os.getenv("CHUNK_SIZE_MB", "95"))
     except ValueError:
         chunk_size_mb = 95
+    timezone = os.getenv("TIMEZONE", "UTC")
     return Settings(
         admin_password=admin_password,
         max_concurrent=maxc,
@@ -81,4 +83,5 @@ def load_settings() -> Settings:
         log_level=log_level,
         chunked_uploads_enabled=chunked_uploads_enabled,
         chunk_size_mb=chunk_size_mb,
+        timezone=timezone,
     )