Add WiFi and HDMI power saving features for remote sensors

Implements power saving optimizations to extend battery life on solar-powered remote air quality sensors:

- WiFi Power Saving: Disable WiFi 10 minutes after boot to save ~100-200mA
  - Configurable via web UI checkbox in admin panel
  - WiFi automatically re-enables after reboot for 10-minute configuration window
  - Systemd timer (nebuleair-wifi-powersave.timer) manages automatic disable
  - New wifi/power_save.py script checks database config and disables WiFi via nmcli

- HDMI Disable: Added hdmi_blanking=2 to boot config to save ~20-30mA
  - Automatically configured during installation

- Database: Added wifi_power_saving boolean config (default: disabled)
  - Uses INSERT OR IGNORE for safe updates to existing installations

- UI: Added checkbox control in admin.html for WiFi power saving
  - Includes helpful description of power savings and behavior

- Services: Updated setup_services.sh and update_firmware.sh to manage new timer

Total power savings: ~120-230mA when WiFi power saving enabled

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

html/admin.html

@@ -118,6 +118,16 @@
                 </label>
               </div>
 
+              <div class="form-check mb-3">
+                <input class="form-check-input" type="checkbox" value="" id="check_wifi_power_saving" onchange="update_config_sqlite('wifi_power_saving', this.checked)">
+                <label class="form-check-label" for="check_wifi_power_saving">
+                  WiFi Power Saving
+                </label>
+                <small class="form-text text-muted d-block ms-4">
+                  Disable WiFi 10 minutes after boot to save power (~100-200mA). WiFi will re-enable after reboot.
+                </small>
+              </div>
+
               <div class="d-flex justify-content-between align-items-center mb-2">
                 <span class="fw-bold">Protected Settings</span>
                 <button type="button" class="btn btn-sm btn-outline-primary" onclick="toggleProtectedSettings()" id="unlockBtn">
@@ -399,6 +409,7 @@ window.onload = function() {
       const checkbox_envea = document.getElementById("check_envea");
       const checkbox_solar = document.getElementById("check_solarBattery");
       const checkbox_noise = document.getElementById("check_NOISE");
+      const checkbox_wifi_power_saving = document.getElementById("check_wifi_power_saving");
 
       checkbox_bme.checked = response["BME280"];
       checkbox_envea.checked = response["envea"];
@@ -406,6 +417,7 @@ window.onload = function() {
       checkbox_nmp5channels.checked = response.npm_5channel;
       checkbox_wind.checked = response["windMeter"];
       checkbox_noise.checked = response["NOISE"];
+      checkbox_wifi_power_saving.checked = response["wifi_power_saving"];
 
       checkbox_uSpot.checked = response["send_uSpot"];
       checkbox_aircarto.checked = response["send_aircarto"];