docs: guide safe first-time and interrupted CloudLinux conversion

[NikolayVoina]

New customers need a clear way to prepare a supported server, recognise an interrupted conversion, and distinguish an OS conversion failure from an optional feature that needs separate setup.

This change adds a preparation checklist and a clean-conversion/recovery decision table, links to feature setup guides, and describes safe checks using the logs already created by cldeploy. It also corrects the Solo FAQ's suggestion that CentOS 8 is a supported direct source, and explains why CentOS 6/7 cannot be converted directly to Solo 8+.

The commands and limitations were checked against the public cldeploy 1.132 script on 2026-09-06. In particular, its precheck is not guaranteed to be non-mutating and it has no --resume option. The guide states those limits explicitly and keeps an escalation boundary for a partial server whose safe recovery path is unknown.

Validation:

• Existing yarn.lock installed with --non-interactive --frozen-lockfile; no dependency changes.
• VuePress production build on Node 22, including all 49 pages.
• All 18 newly added internal links and target anchors checked in generated HTML.
• git diff --check.

Release coordination: keep this PR in draft for product/documentation review. Guidance that promises a non-mutating precheck or gives recorded-resume commands must be published with the release that actually provides those behaviors. This PR does not advertise either as available in 1.132, and does not claim that upgrading a script can recover an old conversion with no recorded state.

[NikolayVoina]

Rechecked this guide against the current development source (cldeploy 1.133) and the publicly downloadable script (1.132) on 2026-09-06. These are not the same release artifact. Both still allow system changes during --precheck, including automatically disabling/removing an enabled Plesk Cgroups Manager without interactive confirmation; neither provides --resume. The guide therefore does not advertise unreleased recovery or non-mutating precheck behavior.

This follow-up corrects that warning, removes an unsupported step-down option, uses the accepted long --help spelling, clarifies edition/component and kernel checks, and points to the existing debug log. Boot warnings must be resolved even when the script exits successfully. The existing Rocky Linux 10 exclusion remains unchanged.

Validation: full VuePress production build on Node 22 (49 pages); all 12 unique added/changed internal destinations and anchors resolve in rendered HTML; git diff --check passes. Existing Browserslist-age and bundle-size warnings only. This was a source/documentation audit, not execution of cldeploy on a server. The reviewed follow-ups change only the two conversion documentation files; the PR remains a draft. Latest head: 090e80e.

The edition follow-up also removes the stale claim that Solo/Admin flags require --skip-registration. The actual handlers in both checked scripts do not impose that restriction. The guide now requires supported OS/panel combinations and a matching activation key or IP-based license; the flags do not grant or change a license. The Admin IP-license example and supported-source examples are consistent with that guidance. The full 49-page build and the same 12 unique internal destinations/anchors were checked again after this follow-up.