Add static DNS (v2 site API) to the legacy adapter

[ChrisonSimtian]

Why

Controller-local DNS records are how a name resolves on the LAN without any public zone being involved, and they were reachable from nothing but curl. Homelab needs them to declare internal names as IaC (Homelab#314) and to stop LAN access to the Pangolin-fronted zones depending on NAT hairpin (Homelab#419).

The v2 surface is not the legacy surface

Static DNS lives on the v2 site API, which shares the host and the auth but none of the conventions:

	legacy …/api/s/<site>	v2 …/v2/api/site/<site>
response	{ "meta": {...}, "data": [...] }	bare JSON array / object
update	partial — send only changed fields	full replacement
a partial PUT	fine	400 Validation failed

Treating them alike compiles and passes every unit test, then fails against a real controller — so the difference is encoded in the types rather than left to a caller to remember. UnifiStaticDnsRecord is non-nullable throughout where the legacy DTOs are nullable: on v2 a partial is not something you can send, and the type shouldn't suggest otherwise. A test pins that every field serializes even at its default value, because the omit-nulls serializer would otherwise quietly thin the body into a rejected partial.

Verified before writing any of it

Probed against the live controller with a throwaway record, then deleted:

POST   -> 200, returns the created record with _id
PUT /{id}  full body     -> 200, replaced
PUT /{id}  partial body  -> 400 Validation failed
DELETE /{id}             -> 200, empty body

Wildcards are supported and match arbitrary labels — *.topaz.local.dev already answers randomtest123.topaz.local.dev on this controller. That's what makes Homelab#419 three records instead of the sixteen it estimated.

Shape

• UnifiLegacyOptions gains Site (parsed from the base URL rather than assumed) and SiteV2Url.
• UnifiLegacySession gains SendAbsoluteAsync — a v2 path can't be reached relative to the legacy base. Auth, TLS handling and the 401 policy are unchanged and shared.
• UnifiLegacyClient gains ListStaticDnsAsync / CreateStaticDnsAsync / UpdateStaticDnsAsync / DeleteStaticDnsAsync.

Unlike rest/user, this one does get a delete: a DNS record carries no history worth preserving, so there's no reversible middle state to prefer.

Tests

36 total, 33 passing / 3 skipped (the destructive ones, correctly gated on session auth). Includes a read-only live test that exercises the whole v2 path against the real controller.

Bumps Chrison.UnifiSharp to 0.3.0. Chrison.UnifiSharp.Api stays at the already-published 10.4.57, so this release has none of the dependency-indexing race 0.2.0 hit.

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