docs: align README with the open-source Community product (#1626)

* docs: align README and overview docs with current AGPLv3 tier model

Community is now described as the complete free product, with a single
consolidated Admiral section replacing scattered per-bullet tags that had
drifted out of sync with the actual gates (security scanning, private
registries, and most of RBAC/audit moved to Community over time). Remove
promotion of Sencho Mesh, Fleet Secrets, and Host Console, which are no
longer discoverable by default. Align the Fleet Secrets, Host Console, and
Sencho Mesh sections in the features overview with the limited-availability
framing already used elsewhere on that page.

Refresh every README screenshot to the current UI and add new captures for
Security, Blueprints, Scheduled Operations, and Compose Doctor.

The introductory tier-framing sentence and docs navigation placement for the
now-hidden surfaces are intentionally left for a later, dedicated pass once
the Admiral positioning work settles.

* docs: restructure README around the open-source Community product

Drop "What Sencho is not (yet)", fold its known-limitations pointer into
the Documentation section. Rewrite Telemetry and data handling to drop the
Admiral license-validation detail, since this file is the open-source
entry point and Admiral customers work from their own agreements. Move
the Admiral section to just before Documentation, community, and license
so the README leads with the Community product throughout.

docs/features/overview.mdx

@@ -152,7 +152,7 @@ Track mutating actions across your Sencho instance with a searchable trail: who
 ## Fleet management
 
 <Frame>
-  <img src="/images/overview/fleet-topology.png" alt="Fleet view in grid layout: the fleet masthead showing aggregate CPU, memory, and container counts across all nodes, the tab strip (Overview, Snapshots, Status, Map, Deployments, Routing, Federation, Actions, Secrets), and the node grid with per-node container counts and CPU, RAM, and disk usage bars." />
+  <img src="/images/overview/fleet-topology.png" alt="Fleet view in grid layout: the fleet masthead showing aggregate CPU, memory, and container counts across all nodes, the tab strip (Overview, Snapshots, Status, Map, Deployments, Federation, Actions), and the node grid with per-node container counts and CPU, RAM, and disk usage bars." />
 </Frame>
 
 ### Multi-node support
@@ -165,7 +165,7 @@ Add remote nodes behind NAT, residential networks, or corporate firewalls withou
 
 ### Sencho Mesh
 
-Connect containers across nodes by hostname over the Pilot tunnel so a multi-node fleet feels like one machine. Opt a stack into the mesh and its services become reachable from any other meshed stack at a stable hostname. Admiral. [Learn more →](/features/sencho-mesh)
+Connect containers across nodes by hostname over the Pilot tunnel so a multi-node fleet feels like one machine. Opt a stack into the mesh and its services become reachable from any other meshed stack at a stable hostname. Limited availability; requires Admiral when enabled on an instance. [Learn more →](/features/sencho-mesh)
 
 ### Fleet View
 
@@ -189,7 +189,7 @@ When several Sencho instances run as a fleet, the control instance is the source
 
 ### Fleet Secrets
 
-Centralized, encrypted, versioned env-var bundles you push to labeled nodes' stacks. Every save bumps a version, and every push records a per-node diff in the audit log using overlay merge semantics. Admiral. [Learn more →](/features/fleet-secrets)
+Centralized, encrypted, versioned env-var bundles you push to labeled nodes' stacks. Every save bumps a version, and every push records a per-node diff in the audit log using overlay merge semantics. Limited availability; requires Admiral and the admin role when enabled on an instance. [Learn more →](/features/fleet-secrets)
 
 ### Fleet-wide backups
 
@@ -205,7 +205,7 @@ When you manage nodes running different Sencho versions, the dashboard detects e
 
 ### Host console
 
-Open an interactive terminal on the host OS directly in the browser with full xterm.js emulation and color support. No SSH client required; admin-only. [Learn more →](/features/host-console)
+Open an interactive terminal on the host OS directly in the browser with full xterm.js emulation and color support. No SSH client required. Limited availability; requires Admiral and the admin role when enabled on an instance. [Learn more →](/features/host-console)
 
 ## Security and access