docs: add Support Matrix section under Get More Help (#764)

* Add Support Matrix section under Get More Help

Adds /help/support-matrix with an overview, NetBird client (split into
per-OS pages following the get-started/install layout), Kubernetes
operator, Terraform provider, and self-hosted sub-sections.

Linux/Windows/macOS pages pre-fill OS version cutoffs derived from the
Go toolchain's minimum OS requirements at each NetBird release's Go
version (sourced from go.mod at release tags). Each derived page carries
a Warning callout marking the values as inferences pending team
confirmation. Mobile/TV pages and the other component pages remain TBD
placeholders.

* Rework Linux support page around client modes

Drops the per-distro TBD table and consolidates the description with the
Warning callout. Splits Linux support by client mode: userspace follows
the Go toolchain's minimum OS requirements; kernel mode depends on the
host's iptables/nftables features. Notes Ubuntu 20.04 as the
end-to-end test floor.


* Add full Linux e2e test matrix to support page

Replaces the single Ubuntu 20.04 floor reference with the full set of
distributions covered by the NetBird team's end-to-end tests: Ubuntu
20.04/22.04/24.04, Debian 12, Rocky Linux 9, and Fedora 41. Ubuntu
20.04 remains called out as the oldest tested release.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

src/components/NavigationDocs.jsx

@@ -821,6 +821,60 @@ export const docsNavigation = [
         href: '/help/troubleshooting-client',
       },
       { title: 'Report bugs and issues', href: '/help/report-bug-issues' },
+      {
+        title: 'Support Matrix',
+        isOpen: false,
+        links: [
+          { title: 'Overview', href: '/help/support-matrix' },
+          {
+            title: 'NetBird Client',
+            href: '/help/support-matrix/netbird-client',
+            isOpen: false,
+            links: [
+              {
+                title: 'Linux',
+                href: '/help/support-matrix/netbird-client/linux',
+              },
+              {
+                title: 'Windows',
+                href: '/help/support-matrix/netbird-client/windows',
+              },
+              {
+                title: 'macOS',
+                href: '/help/support-matrix/netbird-client/macos',
+              },
+              {
+                title: 'iOS',
+                href: '/help/support-matrix/netbird-client/ios',
+              },
+              {
+                title: 'Android',
+                href: '/help/support-matrix/netbird-client/android',
+              },
+              {
+                title: 'Android TV',
+                href: '/help/support-matrix/netbird-client/android-tv',
+              },
+              {
+                title: 'tvOS',
+                href: '/help/support-matrix/netbird-client/tvos',
+              },
+            ],
+          },
+          {
+            title: 'Kubernetes Operator',
+            href: '/help/support-matrix/kubernetes-operator',
+          },
+          {
+            title: 'Terraform Provider',
+            href: '/help/support-matrix/terraform-provider',
+          },
+          {
+            title: 'Self-Hosted',
+            href: '/help/support-matrix/self-hosted',
+          },
+        ],
+      },
     ],
   },
 ]