Prepare stable v1.1.0 and simplify V2 onboarding

[Lash-L]

Prepare 1.1.0 as the stable release of the V2 recovery and multipart NC changes. Remove the obsolete V2 unsupported status so guided pairing progresses through key recovery and completes after MQTT connects.

Remove the separate V2 research page and duplicate Beta testing instructions. V2 uses the normal onboarding flow; keep one practical note about recovery time and the sample counter. Update the confirmed-vacuum list and stable package/add-on versions. Retain Beta at 1.1.0-rc2, mark it currently unused, and document switching to stable without implying that add-on data transfers automatically.

Validation:

• GitHub CI: 212 tests passed and the Linux amd64 Docker image built successfully.
• Local: strict documentation build, source/wheel builds, lockfile check, and built-wheel version metadata passed.
• Regression coverage verifies the admin API and V2 progression through region requests, recovered key, NC registration, and MQTT completion.

After merge, publish a non-prerelease v1.1.0 release to build the stable container image and aliases. The release has not been published.