Release v0.0.5: option help modal, update check, effective config sections

- Config option help: modal with dnsmasq docs, label click/mouseleave
- Update check: background + manual check, nav footer tooltip with last check time
- Effective config: sectioned views (DNS, DHCP, etc.), section toggle
- Version bump to 0.0.5

src/DnsmasqWebUI/Models/Config/UpdateCheckOptions.cs

@@ -0,0 +1,13 @@
+namespace DnsmasqWebUI.Models.Config;
+
+/// <summary>
+/// Options for the periodic update check (GitHub latest release). Bound from "UpdateCheck" config section.
+/// </summary>
+public class UpdateCheckOptions
+{
+    /// <summary>Configuration section name.</summary>
+    public const string SectionName = "UpdateCheck";
+
+    /// <summary>Interval in minutes between checks. Default 1440 (24 hours). Set to 0 to disable periodic checks.</summary>
+    public int IntervalMinutes { get; set; } = 1440;
+}