Move Tailscale, Semaphore, and Gitea to their own top-level pages

Same move as Docker: each was buried inside the generic Integrations
browsing view, sharing one "pick any integration" dropdown across six
unrelated types. Give them dedicated pages instead.

New web/src/pages/{Tailscale,Semaphore,Gitea}.tsx each reuse the
existing, unchanged API routes and adapters (no server changes) with
their own integration picker scoped to just that type. Added matching
nav items (Tailscale, Semaphore, Gitea, right after Docker) and routes.

Removed the corresponding state/handlers/tables from Integrations.tsx
entirely (374 lines). Adding, editing, enabling/disabling, and
deleting each credential itself still happens under Integrations ->
Manage integrations, same as Proxmox and Synology, which stay on the
Integrations page. Selecting one of these three types in Integrations'
generic browsing dropdown now points to its new page instead of
rendering a table there too.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

web/src/layout/AppShell.tsx

@@ -8,6 +8,9 @@ import {
   IconKey,
   IconPlugConnected,
   IconBrandDocker,
+  IconAffiliate,
+  IconPlayerPlay,
+  IconBrandGit,
   IconUsers,
   IconHistory,
   IconSettings,
@@ -30,6 +33,9 @@ const NAV_ITEMS: NavItem[] = [
   { to: "/secrets", label: "Secrets", icon: <IconKey size={20} /> },
   { to: "/integrations", label: "Integrations", icon: <IconPlugConnected size={20} /> },
   { to: "/docker", label: "Docker", icon: <IconBrandDocker size={20} /> },
+  { to: "/tailscale", label: "Tailscale", icon: <IconAffiliate size={20} /> },
+  { to: "/semaphore", label: "Semaphore", icon: <IconPlayerPlay size={20} /> },
+  { to: "/gitea", label: "Gitea", icon: <IconBrandGit size={20} /> },
   { to: "/users", label: "Users", icon: <IconUsers size={20} />, minRole: "admin" },
   { to: "/audit-log", label: "Audit Log", icon: <IconHistory size={20} />, minRole: "operator" },
   { to: "/settings", label: "Settings", icon: <IconSettings size={20} />, minRole: "admin" },