Phase 20: per-container inspect + start/stop/restart, local + agent (0.26.0)

Stack Overview now renders each service as an expandable ContainerCard with a
curated single-container inspect view and admin start/stop/restart buttons,
both for local stacks (GET/POST /api/containers/{id}[/{action}]) and remote
stacks (proxied via /api/agents/{id}/containers/* to the agent's new
/agent/containers/* endpoints). Only compose-managed containers are exposed.

Also bumps version 0.23.0 -> 0.26.0 (the bumps for the already-committed
Phase 18 image-prune / Phase 19 compose-validate were missed) and backfills
README sections for Phase 18/19/20.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

README.md

@@ -153,6 +153,33 @@ as intuitive as Dockge, as capable as Portainer for Compose workflows.
   container or connect any container on the host (`POST /api/networks/{id}/connect`
   / `/disconnect`).
 
+### Phase 20 — Container management
+
+- The stack **Overview** tab now renders each service as an expandable
+  **container card** instead of a static row. Expanding it fetches a curated
+  single-container inspect view (image, state + exit code, restart count,
+  started-at, networks, mounts, and environment) via
+  `GET /api/containers/{id}`.
+- Admins get **per-container start / stop / restart** buttons directly on the
+  card (`POST /api/containers/{id}/{action}`), so a single misbehaving service
+  can be bounced without touching the rest of the stack.
+- Works for **remote stacks** too — the same card is used on the remote stack
+  detail page, proxied through `/api/agents/{id}/containers/*` to the agent's
+  new `/agent/containers/*` endpoints.
+- Only containers carrying the `com.docker.compose.project` label are exposed,
+  so this never becomes a generic "control any container on the host" backdoor.
+
+### Phase 19 — Compose validate & diff
+
+- The editor can **validate** a compose file (`docker compose config`) before
+  deploying and show a **diff against the currently deployed** definition, so
+  you can see exactly what a re-deploy will change.
+
+### Phase 18 — Image prune
+
+- **Prune images** (dangling, or all unused) from the Images page, on the local
+  host and on each agent.
+
 ### Phase 17 — Multi-host dashboard
 
 - The dashboard now shows, **per host** (local + each registered agent, online