feat(api): support Swarm-Tag, Swarm-Pin, Swarm-Deferred-Upload on /soc

[martinconic]

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• I have read the coding guide.
• My change requires a documentation update, and I have done it.
• I have added tests to cover my changes.
• I have filled out the description and linked the related issues.

Description

The POST /soc handler previously hardcoded TagID=0, Pin=false, and
Deferred=false, forcing every SOC upload through the direct-push path
to the target neighborhood. On public networks this commonly takes

15s to return.

Bring /soc to parity with the other upload endpoints by reading and
respecting Swarm-Tag, Swarm-Pin, and Swarm-Deferred-Upload. Resolution
order is conservative to avoid changing existing behavior: an explicit
Swarm-Deferred-Upload value wins, otherwise a non-zero Swarm-Tag opts
the caller into deferred mode (matching /chunks), otherwise the upload
remains direct as before. When a session is in use, the response
echoes the resolved Swarm-Tag header (exposed via CORS).

openapi/Swarm.yaml is updated to document the new request parameters,
the swarm-tag response header, and the 404 response path introduced
by the new "tag not found" handling. Pre-existing spec drift on
402/413/422 for this endpoint is left for a separate alignment pass.

Fixes #5444

Open API Spec Version Changes (if applicable)

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AI Disclosure

• This PR contains code that has been generated by an LLM.
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