feat: air-gapped deployment guide, no implicit downloads

- Ship tiktoken's cl100k_base inside the package and build the encoding
  from it, so token counting never downloads anything.
- Default EMBEDDINGS_CACHE_DIR to <data home>/models instead of FastEmbed's
  temp dir, and read tokenizer.json and repo metadata from that cache, so
  a model downloads once and survives reboots.
- TTS_PROVIDER=none and STT_PROVIDER=none switch the speech features off:
  the endpoints return 404, audio files fail to ingest with a clear
  message, /api/config reports tts_available/stt_available, and the UI
  hides the Speak and microphone buttons.
- Drop the Google Fonts Roboto import from the web UI.
- prefetch-models fills the cache the app reads; verify-offline checks the
  packaged encoding.
- Docs: new Air-Gapped Deployment guide, settings and cache notes.

frontend/src/components/MessageInput.tsx

@@ -30,6 +30,7 @@ import {
   selectSelectedDocs,
   selectSelectedModel,
   selectSourceDocs,
+  selectSttAvailable,
   selectToken,
   setSelectedDocs,
 } from '../preferences/preferenceSlice';
@@ -348,6 +349,7 @@ export default function MessageInput({
   const token = useSelector(selectToken);
   const attachments = useSelector(selectAttachments);
   const selectedModel = useSelector(selectSelectedModel);
+  const sttAvailable = useSelector(selectSttAvailable);
   const unreadableAttachmentIds = useMemo(
     () =>
       new Set(
@@ -1771,7 +1773,7 @@ export default function MessageInput({
                 loading={toolsLoading}
               />
             )}
-            {ENABLE_VOICE_INPUT && (
+            {ENABLE_VOICE_INPUT && sttAvailable && (
               <MicButton
                 recordingState={recordingState}
                 loading={loading}

frontend/src/conversation/ConversationBubble.tsx

@@ -27,6 +27,7 @@ import {
   selectChunks,
   selectSelectedDocs,
   selectToken,
+  selectTtsAvailable,
 } from '../preferences/preferenceSlice';
 import { isToolCallRunning } from '../utils/streamingStatusUtils';
 import AnswerFlow from './AnswerFlow';
@@ -110,6 +111,7 @@ const ConversationBubble = forwardRef<
   // const bubbleRef = useRef<HTMLDivElement | null>(null);
   const chunks = useSelector(selectChunks);
   const selectedDocs = useSelector(selectSelectedDocs);
+  const ttsAvailable = useSelector(selectTtsAvailable);
   const [isEditClicked, setIsEditClicked] = useState(false);
   const [editInputBox, setEditInputBox] = useState<string>('');
   const messageRef = useRef<HTMLDivElement>(null);
@@ -554,9 +556,11 @@ const ConversationBubble = forwardRef<
                         </Button>
                       </div>
                     )}
-                    <div className="relative block items-center justify-center">
-                      <SpeakButton text={message} />
-                    </div>
+                    {ttsAvailable && (
+                      <div className="relative block items-center justify-center">
+                        <SpeakButton text={message} />
+                      </div>
+                    )}
                     {handleFeedback && (
                       <>
                         <div className="relative flex items-center justify-center">

frontend/src/conversation/conversationListener.test.ts

@@ -81,6 +81,8 @@ const makeStore = (
     agentFolders: null,
     roles: [],
     rolesResolved: false,
+    ttsAvailable: true,
+    sttAvailable: true,
   };
   const conversation: ConversationState = {
     queries: [],

frontend/src/hooks/useDataInitializer.ts

@@ -1,6 +1,7 @@
 import { useEffect } from 'react';
 import { useDispatch, useSelector } from 'react-redux';
 
+import userService from '../api/services/userService';
 import {
   getDocs,
   getConversations,
@@ -12,6 +13,7 @@ import {
   setConversations,
   setPrompts,
   setSourceDocs,
+  setSpeechAvailability,
 } from '../preferences/preferenceSlice';
 
 /**
@@ -22,6 +24,7 @@ import {
  * - Fetching and setting up source documents
  * - Fetching and setting up prompts
  * - Fetching and setting up conversations
+ * - Reading which speech features the server has switched on
  *
  * @param isAuthLoading -
  */
@@ -30,6 +33,22 @@ export default function useDataInitializer(isAuthLoading: boolean) {
   const token = useSelector(selectToken);
   const conversations = useSelector(selectConversations);
 
+  // Speech features; /api/config needs no auth.
+  useEffect(() => {
+    userService
+      .getConfig()
+      .then((response) => response.json())
+      .then((config) => {
+        dispatch(
+          setSpeechAvailability({
+            tts: config?.tts_available !== false,
+            stt: config?.stt_available !== false,
+          }),
+        );
+      })
+      .catch(() => undefined);
+  }, [dispatch]);
+
   // Initialize documents
   useEffect(() => {
     // Skip if auth is still loading

frontend/src/index.css

@@ -1,6 +1,3 @@
-@import url('https://fonts.googleapis.com/css2?family=Roboto:wght@300;400;500;700&display=swap')
-layer(base);
-
 @import 'tailwindcss';
 
 @import 'tw-animate-css';
@@ -8,7 +5,6 @@ layer(base);
 @custom-variant dark (&:is(.dark *));
 
 @theme {
-  --font-roboto: Roboto, sans-serif;
   --font-mono:
     'IBMPlexMono-Medium', ui-monospace, SFMono-Regular, Menlo, Consolas,
     monospace;

frontend/src/modals/AgentDetailsModal.tsx

@@ -120,7 +120,7 @@ export default function AgentDetailsModal({
             </div>
             {sharedToken ? (
               <div className="flex flex-col gap-2">
-                <p className="font-roboto dark:text-foreground inline text-sm leading-normal font-medium break-all text-gray-700">
+                <p className="dark:text-foreground inline text-sm leading-normal font-medium break-all text-gray-700">
                   <a
                     href={`${baseURL}/shared/agent/${sharedToken}`}
                     target="_blank"
@@ -172,7 +172,7 @@ export default function AgentDetailsModal({
             {apiKey ? (
               <div className="flex flex-col gap-2">
                 <div className="flex items-center gap-2">
-                  <div className="font-roboto dark:text-foreground text-sm leading-normal font-medium break-all text-gray-700">
+                  <div className="dark:text-foreground text-sm leading-normal font-medium break-all text-gray-700">
                     {apiKey}
                     {!apiKey.includes('...') && (
                       <CopyButton
@@ -231,7 +231,7 @@ export default function AgentDetailsModal({
             </div>
             {webhookUrl ? (
               <div className="flex flex-col gap-2">
-                <p className="font-roboto dark:text-foreground text-sm leading-normal font-medium break-all text-gray-700">
+                <p className="dark:text-foreground text-sm leading-normal font-medium break-all text-gray-700">
                   <a href={webhookUrl} target="_blank" rel="noreferrer">
                     {webhookUrl}
                   </a>

frontend/src/preferences/preferenceSlice.ts

@@ -44,6 +44,10 @@ export interface Preference {
   // not act before the first /me response (avoids a first-paint admin bounce).
   roles: string[];
   rolesResolved: boolean;
+  // Speech features the server has switched on (/api/config). True until the
+  // config loads, so a backend without these flags keeps showing the controls.
+  ttsAvailable: boolean;
+  sttAvailable: boolean;
 }
 
 const initialState: Preference = {
@@ -74,6 +78,8 @@ const initialState: Preference = {
   agentFolders: null,
   roles: [],
   rolesResolved: false,
+  ttsAvailable: true,
+  sttAvailable: true,
 };
 
 export const prefSlice = createSlice({
@@ -142,6 +148,13 @@ export const prefSlice = createSlice({
       state.roles = [];
       state.rolesResolved = false;
     },
+    setSpeechAvailability: (
+      state,
+      action: PayloadAction<{ tts: boolean; stt: boolean }>,
+    ) => {
+      state.ttsAvailable = action.payload.tts;
+      state.sttAvailable = action.payload.stt;
+    },
   },
 });
 
@@ -166,6 +179,7 @@ export const {
   setAgentFolders,
   setRoles,
   clearRoles,
+  setSpeechAvailability,
 } = prefSlice.actions;
 export default prefSlice.reducer;
 
@@ -314,3 +328,7 @@ export const selectRolesResolved = (state: RootState) =>
   state.preference.rolesResolved;
 export const selectIsAdmin = (state: RootState) =>
   state.preference.roles.includes('admin');
+export const selectTtsAvailable = (state: RootState) =>
+  state.preference.ttsAvailable;
+export const selectSttAvailable = (state: RootState) =>
+  state.preference.sttAvailable;

frontend/src/store.ts

@@ -56,6 +56,8 @@ const preloadedState: { preference: Preference } = {
     agentFolders: null,
     roles: [],
     rolesResolved: false,
+    ttsAvailable: true,
+    sttAvailable: true,
   },
 };
 const store = configureStore({