feat!: remove the old API, ports 8081 and 8080 (step 4a)

Step 4a of docs/SECURITY_PLAN.md. Port 80 keeps the eleven HTTP routes of
ADR 0006 and the socket at /ws; everything else moved to protocol 2.

- Port 8081 (ApiRoutes) and the socket on 8080 (SocketEmitter) are gone.
  Protocol 2 owns its frame buffer and loop-task check.
- Port 80 drops every route the old web UI called: reads, edits,
  settings, scans, reboot, /shades.cfg, /discovery. HttpRoutes.cpp holds
  what stays.
- ModelSnapshot, SnapshotSlots and the read documents are gone. The item
  snapshot types stay, as ItemSnapshot, for events, MQTT and the command
  replies.
- Model edits reply only to their protocol 2 op: requestResult goes.
- The settings' toJSON writers, used only by the settings routes, go.
- The _espsomfy_rts._tcp mDNS record moves to port 80, with path=/ws.
- The memory event reports the loop-rate window it closes.
- A deleted room no longer re-publishes its retained MQTT topics.
- e2e: the heap check reads the sync's status; the sync is checked on
  its own instead of against /controller.
- README gets an API and ports section.

BREAKING CHANGE: ports 8081 and 8080 and the old HTTP routes are gone.
Home Assistant needs integration 3.0.0 or newer.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

test/e2e/proto_client.py

@@ -226,7 +226,14 @@ def http_json(host, path, port=80, method="GET", body=None, headers=None, timeou
         return json.loads(r.read())
 
 
-def heap(host):
-    """free, min and uptime from /discovery on 8081 (protocol 1, until it goes)."""
-    m = http_json(host, "/discovery", port=8081)["memory"]
-    return {"free": m["free"], "min": m["min"], "max": m["max"], "uptime": m["uptime"]}
+def heap(host, token=None):
+    """free, min, max and uptime from the status in a sync."""
+    c = ProtoClient(host, params={"apikey": token} if token else None)
+    try:
+        schema = Schema()
+        _, frames, _ = run_sync(c, schema)
+    finally:
+        c.close()
+    key = schema.keys["status"]
+    status = schema.expand(next(f["d"][key] for f in frames if key in f["d"]))
+    return {"free": status["freeHeap"], "min": status["minHeap"], "max": status["maxHeap"], "uptime": status["uptime"]}