Feature: DPA N-Series (#372)

* Feature: DPA N-Series support

Connects to N-Series receivers (e.g. N-DR1) via OSC over TCP.
Displays audio level, RF strength (A/B), battery status and
warnings for both channels.

* Add Lato font (bundled, offline-safe) to DPA plugin

* Add DPA plugin icon

* Fix: TCP framing, correct meter scaling

- Fix osc-tcp connection type being caught by osc SLIP handler in device.js
- Add subscriptions for tx/active, tx/name, tx/batterystatus
- Fix audio meter formula direction (was inverted)
- Scale audiolevel and rfstrength by /10 (values are dB×10)

* Fix: CSS

plugins/dpa/info.html

@@ -0,0 +1,8 @@
+<h2>DPA N-Series Digital Wireless</h2>
+<p>Connects to a DPA N-Series wireless receiver (e.g. N-DR1) via OSC over TCP.</p>
+<ul>
+  <li>Default TCP port: <strong>1993</strong> (configurable on device)</li>
+  <li>Shows both channels with audio level, RF strength (A/B), battery status and active warnings</li>
+  <li>Audio level, RF strength and battery data are read from the device via OSC subscriptions and <code>/settings/retrieve</code></li>
+</ul>
+<p>Enable TCP control on the device under <em>Advanced → LAN</em>.</p>