Move AP credentials to config and clarify STA UI access

README.md

@@ -249,13 +249,14 @@ inline constexpr uint16_t EXPECTED_SENDER_IDS[NUM_SENDERS] = { 0xF19C };
 - Uses deep sleep between cycles (`SENDER_WAKE_INTERVAL_SEC`).
 
 ## Web UI
-- AP SSID: `DD3-Bridge-<short_id>`
-- AP password: `changeme123`
+- AP SSID: `DD3-Bridge-<short_id>` (prefix configurable)
+- AP password: `changeme123` (configurable)
 - Endpoints:
   - `/`: status overview
   - `/wifi`: WiFi/MQTT/NTP config (AP and STA)
   - `/sender/<device_id>`: per-sender details
 - Sender IDs on `/` are clickable (open sender page in a new tab).
+- In STA mode, the UI is also available via the board’s IP/hostname on your WiFi network.
 
 ## MQTT
 - Topic: `smartmeter/<deviceId>/state`