feat: 添加站点设置中的 favicon URL 支持，更新相关接口和页面

backend/migration/src/lib.rs

@@ -47,6 +47,7 @@ mod m20260402_000036_create_worker_jobs;
 mod m20260402_000037_add_wechat_share_qr_setting_to_site_settings;
 mod m20260402_000038_add_music_enabled_to_site_settings;
 mod m20260402_000039_add_maintenance_mode_to_site_settings;
+mod m20260403_000040_add_favicon_url_to_site_settings;
 pub struct Migrator;
 
 #[async_trait::async_trait]
@@ -98,6 +99,7 @@ impl MigratorTrait for Migrator {
             Box::new(m20260402_000037_add_wechat_share_qr_setting_to_site_settings::Migration),
             Box::new(m20260402_000038_add_music_enabled_to_site_settings::Migration),
             Box::new(m20260402_000039_add_maintenance_mode_to_site_settings::Migration),
+            Box::new(m20260403_000040_add_favicon_url_to_site_settings::Migration),
             // inject-above (do not remove this comment)
         ]
     }

backend/migration/src/m20260403_000040_add_favicon_url_to_site_settings.rs

@@ -0,0 +1,45 @@
+use sea_orm_migration::prelude::*;
+
+#[derive(DeriveMigrationName)]
+pub struct Migration;
+
+#[async_trait::async_trait]
+impl MigrationTrait for Migration {
+    async fn up(&self, manager: &SchemaManager) -> Result<(), DbErr> {
+        let table = Alias::new("site_settings");
+
+        if !manager.has_column("site_settings", "seo_favicon_url").await? {
+            manager
+                .alter_table(
+                    Table::alter()
+                        .table(table.clone())
+                        .add_column(
+                            ColumnDef::new(Alias::new("seo_favicon_url"))
+                                .string()
+                                .null(),
+                        )
+                        .to_owned(),
+                )
+                .await?;
+        }
+
+        Ok(())
+    }
+
+    async fn down(&self, manager: &SchemaManager) -> Result<(), DbErr> {
+        let table = Alias::new("site_settings");
+
+        if manager.has_column("site_settings", "seo_favicon_url").await? {
+            manager
+                .alter_table(
+                    Table::alter()
+                        .table(table)
+                        .drop_column(Alias::new("seo_favicon_url"))
+                        .to_owned(),
+                )
+                .await?;
+        }
+
+        Ok(())
+    }
+}