fix: add missing <string> and <vector> includes to HostPlatformColor.h (#2889)

## Summary
- `HostPlatformColor.h` uses `std::string` (in `ColorWithSystemEffect`
struct and `createSemanticColor` declaration) and
`std::vector<std::string>` but did not include the `<string>` or
`<vector>` headers.
- This causes build failures when this header is included before any
other header that transitively pulls in those standard library headers
(e.g. via `PointerHoverTracker.cpp`).
- Adds the missing `#include <string>` and `#include <vector>`.

## Test plan
- [x] Verified the build error is resolved with this change

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: Saadnajmi

packages/react-native/ReactCommon/react/renderer/graphics/platform/ios/react/renderer/graphics/HostPlatformColor.h

@@ -10,6 +10,8 @@
 #include <react/renderer/graphics/ColorComponents.h>
 #include <react/utils/hash_combine.h>
 #include <cmath>
+#include <string>
+#include <vector>
 
 namespace facebook::react {