feat(auth): make OAuth credentials user-specific via UserIntegration records

Setup pages now accept an integration_id query param to save OAuth
credentials to the user's personal UserIntegration record instead
of global settings. The integrations dashboard shows an "Authorize"
button for OAuth types (Dropbox, Google Drive, OneDrive) that need
credentials.

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

tests/test_views_dropbox.py

@@ -26,3 +26,21 @@ class TestDropboxViews:
         """Test the Dropbox OAuth callback with auth code."""
         response = client.get("/dropbox-callback?code=test_code")
         assert response.status_code == 200
+
+    def test_dropbox_setup_page_with_integration_id(self, client):
+        """Test the Dropbox setup page accepts integration_id query param."""
+        response = client.get("/dropbox-setup?integration_id=42")
+        assert response.status_code == 200
+        # The template should store the integration_id for per-user OAuth flow
+        assert b"oauth_integration_id" in response.content
+        assert b"42" in response.content
+
+    def test_dropbox_setup_page_without_integration_id(self, client):
+        """Test the Dropbox setup page works without integration_id (global flow)."""
+        response = client.get("/dropbox-setup")
+        assert response.status_code == 200
+        # The template should not set integration_id when not provided
+        body = response.text
+        assert "oauth_integration_id" in body  # The JS code is always present
+        # But integration_id template var should be empty
+        assert 'const integrationId = ""' in body