Document iteration 1: settings file, HA Dashboard tab, new hooks

README: settings file, --config, the new tab. ARCHITECTURE.md and
CLAUDE.md: prepare() hook, app command-line options, app code layout,
WebEngine notes, the moc raw-string pitfall. THIRD_PARTY_NOTICES: Qt
WebEngine. Ship config.example.json; the package README explains the
set-up. PROGRESS.md and DESIGN.md: phase 3 results and deviations.

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

resources/config.example.json

@@ -0,0 +1,20 @@
+{
+  "device": {
+    "name": "Steam Frame"
+  },
+  "mqtt": {
+    "host": "homeassistant.local",
+    "port": 1883,
+    "username": "frameassistant",
+    "password": "change-me",
+    "tls": {
+      "enabled": false
+    }
+  },
+  "homeassistant": {
+    "url": "http://homeassistant.local:8123"
+  },
+  "notifications": {
+    "timeout_s": 10
+  }
+}