Add Firmware 20.0.0-21.0.0 IPC support and stubs

This commit implements comprehensive firmware 20.0.0 through 21.0.0
support for Citron, including:

- Updated firmware version constants to 21.0.0 in api_version.h
- Updated HID service firmware version string to 21.0.0
- Added IPC command stubs for firmware 20.0.0+ in:
  * ISystemSettingsServer (commands 263, 264, 282, 283, 289, 300, 301, 306, 307)
  * IFirmwareDebugSettingsServer (command 24)
  * IApplicationFunctions (command 330)
  * IOlscServiceForSystemService (command 914)
  * IRemoteStorageController (commands 28, 901)
  * IService (migration) (commands 2250, 2260)
  * IAudioController (command 10200)

- Created new service interfaces with proper stubs:
  * IContinuousRecorder (grcsrv) - command 5 [20.2.0+] with 0x20-byte input
  * IDownloadContext (news) - command 4 [20.0.0+]
  * INotifyService (pdm:ntfy) - commands 100, 101 [20.0.0+] returning outinterfaces

- Added all new source files to CMakeLists.txt build system
- Fixed logging tag usage (Service_Migration instead of Service_MIG)
- Added required CMIF serialization headers for proper template instantiation

All stubs return success explicitly, eliminating the need for auto-stubbing.
All implementations follow Switchbrew documentation as closely as possible.

Based on Switchbrew documentation:
- https://switchbrew.org/wiki/21.0.0
- https://switchbrew.org/wiki/20.5.0
- https://switchbrew.org/wiki/20.4.0
- https://switchbrew.org/wiki/20.3.0
- https://switchbrew.org/wiki/20.2.0
- https://switchbrew.org/wiki/20.1.5
- https://switchbrew.org/wiki/20.1.1
- https://switchbrew.org/wiki/20.1.0
- https://switchbrew.org/wiki/20.0.1
- https://switchbrew.org/wiki/20.0.0

Signed-off-by: Zephyron <zephyron@citron-emu.org>

src/core/hle/service/ns/ns.cpp

@@ -3,6 +3,7 @@
 
 #include "core/hle/service/ns/develop_interface.h"
 #include "core/hle/service/ns/ns.h"
+#include "core/hle/service/ns/notify_service.h"
 #include "core/hle/service/ns/platform_service_manager.h"
 #include "core/hle/service/ns/query_service.h"
 #include "core/hle/service/ns/service_getter_interface.h"
@@ -33,6 +34,7 @@ void LoopProcess(Core::System& system) {
     server_manager->RegisterNamedService("ns:vm",
                                          std::make_shared<IVulnerabilityManagerInterface>(system));
     server_manager->RegisterNamedService("pdm:qry", std::make_shared<IQueryService>(system));
+    server_manager->RegisterNamedService("pdm:ntfy", std::make_shared<INotifyService>(system));
 
     server_manager->RegisterNamedService("pl:s",
                                          std::make_shared<IPlatformServiceManager>(system, "pl:s"));