feat(webui): Volume settings section and admin boost-cap editor

Adds a server-backed Volume card to page settings with horn, TTS, and
microphone sliders. Each slider is a 0-100% share of the ceiling the
server resolved for that user, and the card shows the resulting
multiplier plus whether the user is on the normal global limit or a
raised VIP limit. A slider whose ceiling is zero renders disabled rather
than pretending to do something.

The admin section gains sliders for the VIP boost hard caps beside the
existing global gains. Both editors now render from one GAIN_FIELDS list
through a shared GainSlider instead of six copied slider blocks.

Includes the rebuilt bundle so the served UI matches the source.

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

webui/src/components/SettingsPanel/index.jsx

@@ -12,6 +12,7 @@ import Tabs, { Tab, TabList, TabPanel, TabPanels } from '../Tabs/index.jsx';
 import SessionSnapshot from '../SessionSnapshot/index.jsx';
 import SocketLogPanel from '../SocketLogPanel/index.jsx';
 import CardFrame from '../CardFrame/index.jsx';
+import VolumeSettingsCard from '../VolumeSettingsCard/index.jsx';
 import KeyPill from '../vip/VipAudioUploadCard/KeyPill.jsx';
 import { useHudMapSetting } from '../../hooks/useHudMapSetting.js';
 import { useSettingsNamespace } from '../../settings/index.js';
@@ -468,6 +469,9 @@ export default function SettingsPanel() {
                 Lowers rover audio only while the main brush is running.
               </SettingHelp>
             </CardFrame>
+            {/* Volume is server-backed rather than cookie-backed: it changes what the
+                rover plays for everyone in the room, so the server owns the limits. */}
+            <VolumeSettingsCard />
             <CardFrame title="Connection" bodyClassName="space-y-1 p-1 text-sm">
               <SettingRow>
                 <span className="font-semibold text-white">Transport</span>