fix(ci): publish dotnet packages only from final release tags

[Fatorin]

Which issue does this PR close?

Closes #8310.

Rationale for this change

The "Determine version suffix" step in release_dotnet.yml recognises final and rc release tags only when the run is a push event.

The release automation now pushes final tags with GITHUB_TOKEN and dispatches the workflow on the tag, so the run arrives as workflow_dispatch, falls through to the manual release_type branch, and packs preview.<run_number>.

For v0.59.2 this published Apache.OpenDAL 0.2.2-preview.78 instead of 0.2.2, and every later automated release would do the same.

The release_type input that produced preview and rc packages predates the automation and is the only path in the repository that pushes an unvoted build to a public registry, so this PR removes it together with the fix.

What changes are included in this PR?

• release_dotnet.yml: the ref alone decides the suffix. An -rc.N tag packs rc.N, a final tag packs the version from OpenDAL.csproj with no suffix, and any other ref packs preview.<run_number>. The publish job runs only for final tags; every other build stays a workflow artifact.
• release_dotnet.yml: remove the release_type dispatch input and the manual prerelease publishing path.
• scripts/release_lifecycle.py, weekly_release.yml, website/community/release/weekly.md: stop passing release_type=none when dispatching the .NET workflow.

Verified by running the suffix step's script locally for push, workflow_dispatch, and pull_request against final tags, rc tags, main, and a merge ref; only non-tag refs produce preview.N. scripts/test_release_lifecycle.py passes except test_real_git_signed_final_refs, which fails on Windows before this change because it hard-codes /tmp.

Are there any user-facing changes?

No change for package consumers. Release managers can no longer publish a preview or rc NuGet package by manual dispatch; a dispatch on a non-tag ref only produces a workflow artifact. Older rc tags still declare the input with default: none, so dispatching them without the argument keeps working.

Breaking changes

AI Usage Statement

• Harness: Claude Code (desktop app)
• Model: Claude Fable 5.1 (claude-fable-5-1)
• Effort: high
• Role: Traced the v0.59.2 workflow run and the release lifecycle script to locate the cause, drafted the changes and this description, and simulated the suffix step locally; the author decided to remove the manual prerelease path and reviewed the diagnosis and the changes. Assumption affecting review: GitHub applies an input's default when a dispatch omits it, so old tags whose workflow still declares release_type accept the argument-less dispatch. actionlint is not installed locally, so the workflows rely on the CI lint.