profilestore: Add unimplemented WriteArrow RPC

[brancz]

Summary

• Adds a new WriteArrow unary RPC to the ProfileStoreService that accepts an Arrow IPC buffer as a single bytes field
• The implementation reads the IPC buffer and logs the number of rows per record batch at debug level, then returns Unimplemented to the client
• Includes all generated protobuf, gRPC gateway, vtprotobuf, TypeScript client, and Swagger code

Test plan

• Verify the server starts and registers the new RPC
• Send an Arrow IPC buffer to the endpoint and confirm row counts are logged
• Confirm the client receives an Unimplemented status code

🤖 Generated with Claude Code

[alwaysmeticulous]

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_{Expected differences? Click here. Last updated for commit 64062f4. This comment will update as new commits are pushed.}