test: add comprehensive tests for critical untested files and fix deprecated warnings

- Add tests for migrate_logs_to_steps.py, upload_to_paperless.py, dropbox API,
  upload_to_dropbox.py, upload_to_nextcloud.py, upload_to_onedrive.py,
  upload_with_rclone.py, and config_validator.py
- Fix PydanticDeprecatedSince20: @validator → @field_validator in config.py, url_upload.py
- Fix PydanticDeprecatedSince20: class Config → model_config = SettingsConfigDict
- Fix PydanticDeprecatedSince211: filter Pydantic internals in settings_display.py
- Fix MovedIn20Warning: use sqlalchemy.orm.declarative_base instead of ext.declarative

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

app/api/url_upload.py

@@ -12,7 +12,7 @@ from typing import Optional
 
 import requests
 from fastapi import APIRouter, HTTPException, Request
-from pydantic import BaseModel, HttpUrl, validator
+from pydantic import BaseModel, HttpUrl, field_validator
 
 from app.auth import require_login
 from app.config import settings
@@ -31,7 +31,8 @@ class URLUploadRequest(BaseModel):
     url: HttpUrl
     filename: Optional[str] = None
 
-    @validator("url")
+    @field_validator("url")
+    @classmethod
     def validate_url_scheme(cls, v):
         """Ensure only HTTP/HTTPS schemes are allowed"""
         parsed = urllib.parse.urlparse(str(v))