fix(selfhost): branding image origins and theme colour (#3389)

fluxer_admin/openapi-admin.json

@@ -11905,7 +11905,11 @@
 									"logo_url": {"nullable": true, "type": "string", "maxLength": 2048},
 									"wordmark_url": {"nullable": true, "type": "string", "maxLength": 2048},
 									"favicon_url": {"nullable": true, "type": "string", "maxLength": 2048},
-									"theme_color": {"nullable": true, "type": "string", "maxLength": 64},
+									"theme_color": {
+										"nullable": true,
+										"type": "string",
+										"pattern": "^(?:#?(?:[0-9a-fA-F]{3}|[0-9a-fA-F]{6}))?$"
+									},
 									"status_page_url": {"nullable": true, "type": "string", "maxLength": 2048},
 									"status_page_incident_history_url": {"nullable": true, "type": "string", "maxLength": 2048},
 									"premium_product_name": {"nullable": true, "type": "string", "minLength": 1, "maxLength": 40},

fluxer_admin/src/templates/pages/instance_config.rs

@@ -950,9 +950,9 @@ fn app_public_config_section(
                             ))
                             (text_input(
                                 "app_theme_color",
-                                "Theme Color",
+                                "Theme Color (hex)",
                                 app_public.branding.theme_color.as_deref().unwrap_or(""),
-                                "#5865f2",
+                                "#4641d9",
                             ))
                         }
                         div class="grid grid-cols-1 gap-4 sm:grid-cols-2" {