Add user-configurable PostgreSQL backup system

Introduced backup/restore via external pg_dump/pg_restore tools, configurable in database.xml. Added DatabaseBackupOptions, PostgresBackupService, and example/config docs. Backup features are enabled only for local databases; remote DBs require manual management. Logging and documentation clarify external tool usage, error handling, and security. Updated provider logic and assembly files accordingly.

src/Jellyfin.CodeAnalysis/obj/Debug/netstandard2.0/Jellyfin.CodeAnalysis.AssemblyInfo.cs

@@ -14,7 +14,7 @@ using System.Reflection;
 [assembly: System.Reflection.AssemblyCompanyAttribute("Jellyfin.CodeAnalysis")]
 [assembly: System.Reflection.AssemblyConfigurationAttribute("Debug")]
 [assembly: System.Reflection.AssemblyFileVersionAttribute("1.0.0.0")]
-[assembly: System.Reflection.AssemblyInformationalVersionAttribute("1.0.0+534b0cde918839aca165b7bd2b1c7df761aca82c")]
+[assembly: System.Reflection.AssemblyInformationalVersionAttribute("1.0.0+43cdbf9b350e608dce121070d565cdce0aea6b17")]
 [assembly: System.Reflection.AssemblyProductAttribute("Jellyfin.CodeAnalysis")]
 [assembly: System.Reflection.AssemblyTitleAttribute("Jellyfin.CodeAnalysis")]
 [assembly: System.Reflection.AssemblyVersionAttribute("1.0.0.0")]

src/Jellyfin.CodeAnalysis/obj/Debug/netstandard2.0/Jellyfin.CodeAnalysis.AssemblyInfoInputs.cache

@@ -1 +1 @@
-16d1d32a5e6e4b7472006b4665d10d7735bf11c7602c8304312d34d2b63afa7f
+bdef8325a5a74be1c67e80979e05ef8eaf8569901dd2077003e91c35b6d8e7dd