fix(drone): conform to established SPA patterns throughout

- Device population: move refreshDroneDevices() inline to index.html
  (same pattern as refreshTscmDevices) and call it from switchMode
  alongside DroneMode.init(); remove _refreshDevices/populateSelect
  from drone.js which was never guaranteed to run before lazy-load
  completed, causing selects to stay on "Loading…" permanently

- IIFE pattern: change from named IIFE + window.DroneMode assignment
  to var DroneMode = (function(){...return{...}})() matching OOK/
  SpyStations convention

- Init guard: add _initialized flag (OOK state.initialized pattern);
  re-entry after destroy() re-registers map/SSE cleanly without
  duplicating click listeners on every mode switch

- Lifecycle: destroy() resets _initialized = false so map and SSE
  are correctly rebuilt on re-entry

- Stop phase: add isDroneRunning tracking variable in index.html;
  _setRunningUI() syncs it; switchMode stop phase now POSTs
  /drone/stop when leaving drone mode while active, matching TSCM

- /drone/devices: add monitor_capable field to WiFi interfaces,
  add running_as_root and warnings array to response (mirrors
  /tscm/devices shape); add os import; show privilege warning div
  in drone.html when not running as root

- drone.html: remove for= attribute from SDR label (plain <label>
  inside .form-group matches TSCM convention); add droneDeviceWarnings
  div for privilege warnings

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

templates/partials/modes/drone.html

@@ -19,7 +19,7 @@
     <div class="section">
         <h3>WiFi Interface</h3>
         <div class="form-group">
-            <label for="droneWifiIface">Interface (monitor mode)</label>
+            <label>Interface (monitor mode)</label>
             <select id="droneWifiIface">
                 <option value="">Loading interfaces…</option>
             </select>
@@ -29,7 +29,7 @@
     <div class="section">
         <h3>SDR Settings</h3>
         <div class="form-group">
-            <label for="droneRtlIndex">RTL-SDR Device (433 MHz)</label>
+            <label>RTL-SDR Device (433 MHz)</label>
             <select id="droneRtlIndex">
                 <option value="">Loading devices…</option>
             </select>
@@ -42,6 +42,8 @@
         </div>
     </div>
 
+    <div id="droneDeviceWarnings" class="info-text" style="display:none; color:var(--accent-yellow); font-size:10px; padding: 0 4px;"></div>
+
     <div class="section">
         <div style="display:flex; gap:8px;">
             <button id="droneStartBtn" class="run-btn" style="flex:1;">Start</button>