docs: document milvus tls environment variables

[amr-sheriff]

Summary

Documents the three new environment variables introduced in PR 36265

Variable	Purpose
MILVUS_SECURE	Enable one-way TLS to Milvus.
MILVUS_SERVER_PEM_PATH	Path to the Milvus server certificate (PEM).
MILVUS_SERVER_NAME	TLS SNI / server name to verify against the certificate.

Updated in all three locales (en/, ja/, zh/).

[RiskeyL]

@amr-sheriff Thanks for catching the new Milvus TLS options and writing these up.

Before we merge, there's one upstream step. Our docs site treats the .env.example files in langgenius/dify as the source of truth for self-host variables. MILVUS_SECURE, MILVUS_SERVER_PEM_PATH, and MILVUS_SERVER_NAME were added to the Pydantic config in #36265 but aren't in any .env.example yet, so for now they live only in code.

Since you're closest to the original change, would you mind opening a quick follow-up PR on langgenius/dify to surface the three in the appropriate .env.example? You'll know best where they fit alongside the existing Milvus vars.

One heads-up on timing: the docs track released versions, so I'll merge this once the upstream change has both landed and shipped in a Dify release, not just merged to main. Link the upstream PR back here and I'll keep this one open to track it. Thanks again for the contribution.