docs(transfer): document standalone load service (#1040)

[jlon]

Summary

Document standalone Transfer deployment, configuration, CLI routing, and operations for Load and Export.

Issue Describe / Design

Related to #1040.

Transfer remains disabled by default, preserving the legacy Master path. When enabled, normal cv load and cv export commands select Transfer directly. The documentation describes the required MySQL production store, Helm endpoint inference, cutover sequence, and compatible status and cancel commands.

Changes

Module / File	Change	Impact on existing behavior
2-Deploy/.../03-conf.md	Add Transfer configuration, defaults, startup, and cutover guidance.	Documents disabled legacy mode and enabled Transfer mode.
2-Deploy/.../01-k8s-Deployment.md	Add Helm deployment and parameter references.	No chart behavior change.
3-User-Manuals/2-Operations/02-cli.md	Document cv export, Transfer routing, and cv transfer operations.	Normal CLI syntax remains unchanged.
3-User-Manuals/1-Key-Features/02-cache.md	Explain automatic-cache routing through Transfer.	No runtime behavior change.
Chinese mirrors	Keep Chinese deployment, configuration, CLI, and cache guidance aligned.	None.

Test verified

Test case	Result	Notes
git diff --check	PASS	No whitespace errors.
npm run build	PASS	English and Chinese Docusaurus sites built successfully. Existing blog, anchor, and Browserslist warnings remain.

Dependencies

• Related PRs: fix(oss-hdfs): correct async start-status checks (#1376) curvine#1411, fix(opendal): declare logging dependency (#1361) curvine#1412, feat(runtime): deploy standalone transfer service (#1040) curvine-helm#52
• Related issues: #1040
• Blocks / blocked by: Production Helm rollout requires an official Curvine image release containing Transfer.