feat(pricing): collapse to two tiers (#1309)

* feat(pricing): collapse to two tiers (Community + Admiral)

Collapse Sencho's pricing from three tiers (Community / Skipper / Admiral)
to two: a generous free Community tier and a single paid Admiral tier. The
Skipper tier is removed.

Now free in Community: auto-heal, auto-update, scheduled operations,
webhooks, notification routing, Fleet Actions and bulk operations, SSO
preset providers (Google / GitHub / Okta), unlimited users with admin and
viewer roles, and deploy safety (atomic deploys, auto-rollback, and
one-click rollback).

Admiral (paid) is focused on running and governing a fleet: blueprints,
Fleet Secrets, deploy enforcement, vulnerability report export, audit log,
host console, private registries, mesh networking, node cordon, managed
cloud backup, LDAP / Active Directory SSO, and the advanced RBAC roles
(deployer, node-admin, auditor) with per-resource scoped assignments.

Internally the license variant distinction is removed so tier is binary
(community / paid). License validation still verifies the Lemon Squeezy
store and product before granting paid status.

Docs and the contributor guide are updated to the two-tier model.

* docs(pricing): correct licensing page to two-tier pricing and tidy stale tier wording

The licensing docs page kept the old Admiral pricing plus a Founder
Lifetime column and an Enterprise paragraph after the two-tier collapse.
Update it to $12/month or $99/year, drop the lifetime and Enterprise
content, and link to the pricing page for current pricing.

Also fix stale "Skipper" wording in CLA.md, SUPPORT.md, one test title,
and three test comments. Historical CHANGELOG entries and the
retired-Skipper license-guard test are intentionally left as-is.

* docs: align licensing and SSO pages with the two-tier model

Correct the SSO overview so the Google, GitHub, and Okta presets read as
available on every tier, matching the provider table; only LDAP and Active
Directory require Sencho Admiral. Remove the lifetime-plan references from the
licensing, settings, and troubleshooting pages so they reflect subscription-only
Admiral pricing.

* fix(rbac): omit scoped permissions from /me on the Community tier

Scoped role assignments only take effect on the paid tier, but GET /api/permissions/me returned them unconditionally, so a downgraded instance with leftover assignments rendered per-resource affordances the API then rejected with 403. The endpoint now mirrors the permission middleware and includes scoped permissions only on the paid tier. Adds a regression test covering the downgrade case.

* docs: use custom-pricing wording on the contact page

The two-tier model has no Enterprise tier; reword the contact page's enterprise pricing/deals to custom pricing/deals so it does not imply a tier that no longer exists.

docs/features/webhooks.mdx

@@ -4,7 +4,7 @@ description: Trigger stack actions from CI/CD pipelines via HTTP webhooks with H
 ---
 
 <Note>
-  Webhooks require a **Skipper** or **Admiral** license. Managing webhooks is admin-only.
+  Managing webhooks is admin-only.
 </Note>
 
 Sencho webhooks let external systems trigger stack actions over HTTP. The typical use case: your CI pipeline builds a new image, then calls a Sencho webhook to deploy the updated stack, with no manual intervention required.
@@ -163,7 +163,7 @@ Sencho retains the last 100 executions per webhook and surfaces the 20 most rece
 
 <AccordionGroup>
   <Accordion title="I don't see Webhooks in Settings.">
-    The page requires a **Skipper** or **Admiral** license. If you are on a paid tier but the node switcher in the top-left shows a remote node, switch to **Local** to reveal the page.
+    Webhooks are managed on the local node. If the node switcher in the top-left shows a remote node, switch to **Local** to reveal the page.
   </Accordion>
 
   <Accordion title="My trigger returns 404 'Webhook not found or signature invalid'.">