feat(drone): replace freeform inputs with populated device selects

Add /drone/devices endpoint that enumerates available WiFi interfaces
(via iw/iwconfig) and RTL-SDR devices (via SDRFactory.detect_devices),
matching the pattern used by TSCM.

Sidebar WiFi interface and RTL-SDR inputs are now <select> elements
populated on init() from /drone/devices, consistent with how other
modes expose hardware selection. HackRF checkbox remains as a toggle
since it's a binary capability rather than an enumerated device list.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

templates/partials/modes/drone.html

@@ -20,15 +20,19 @@
         <h3>WiFi Interface</h3>
         <div class="form-group">
             <label for="droneWifiIface">Interface (monitor mode)</label>
-            <input type="text" id="droneWifiIface" placeholder="e.g. wlan0mon">
+            <select id="droneWifiIface">
+                <option value="">Loading interfaces…</option>
+            </select>
         </div>
     </div>
 
     <div class="section">
         <h3>SDR Settings</h3>
         <div class="form-group">
-            <label for="droneRtlIndex">RTL-SDR Device Index (433 MHz)</label>
-            <input type="number" id="droneRtlIndex" value="0" min="0" max="7" placeholder="Device index">
+            <label for="droneRtlIndex">RTL-SDR Device (433 MHz)</label>
+            <select id="droneRtlIndex">
+                <option value="">Loading devices…</option>
+            </select>
         </div>
         <div class="form-group">
             <label class="inline-checkbox">