fix: palette changes now propagate immediately via ThemeContext

Replace useSetting()-based useTheme() with a React context (ThemeProvider
+ useTheme/usePaletteControl). The context holds palette key in state so
pressing a palette button in Settings re-renders all screens instantly.
Persists to SQLite and reloads the stored value on mount.

mobile/ThemeContext.tsx

@@ -0,0 +1,51 @@
+import { createContext, useContext, useEffect, useState } from 'react';
+import { useSQLiteContext } from 'expo-sqlite';
+import { getSetting, setSetting } from '@/db/queries';
+import { autoKey, PALETTES, type PaletteKey, type Theme } from '@/theme';
+
+type ThemeCtx = {
+  theme: Theme;
+  paletteKey: PaletteKey;
+  setPaletteOverride: (key: PaletteKey) => void;
+};
+
+const ThemeContext = createContext<ThemeCtx>({
+  theme: PALETTES.default,
+  paletteKey: 'auto',
+  setPaletteOverride: () => {},
+});
+
+export function ThemeProvider({ children }: { children: React.ReactNode }) {
+  const db = useSQLiteContext();
+  const [paletteKey, setPaletteKey] = useState<PaletteKey>('auto');
+
+  useEffect(() => {
+    getSetting(db, 'palette_override').then(val => {
+      if (val) setPaletteKey(val as PaletteKey);
+    });
+  // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, []);
+
+  function setPaletteOverride(key: PaletteKey) {
+    setPaletteKey(key);
+    setSetting(db, 'palette_override', key);
+  }
+
+  const resolved = paletteKey === 'auto' ? autoKey() : paletteKey;
+  const theme = PALETTES[resolved as keyof typeof PALETTES] ?? PALETTES.default;
+
+  return (
+    <ThemeContext.Provider value={{ theme, paletteKey, setPaletteOverride }}>
+      {children}
+    </ThemeContext.Provider>
+  );
+}
+
+export function useTheme(): Theme {
+  return useContext(ThemeContext).theme;
+}
+
+export function usePaletteControl(): Pick<ThemeCtx, 'paletteKey' | 'setPaletteOverride'> {
+  const { paletteKey, setPaletteOverride } = useContext(ThemeContext);
+  return { paletteKey, setPaletteOverride };
+}

mobile/app/(tabs)/settings.tsx

@@ -5,7 +5,8 @@ import {
   Text, TextInput, View,
 } from 'react-native';
 import { deleteRemoteActivities, getSetting, setSetting, useSetting } from '@/db/queries';
-import { PALETTES, type PaletteKey, useTheme } from '@/theme';
+import { PALETTES, type PaletteKey } from '@/theme';
+import { useTheme, usePaletteControl } from '@/ThemeContext';
 
 export default function SettingsScreen() {
   const db = useSQLiteContext();
@@ -24,8 +25,7 @@ export default function SettingsScreen() {
   const [syncUpload,  setSyncUpload]  = useState(storedSyncUpload);
   const [saved,       setSaved]       = useState(false);
   const theme = useTheme();
-  const storedPalette = (useSetting('palette_override') ?? 'auto') as PaletteKey;
-  const [palette, setPalette] = useState<PaletteKey>(storedPalette);
+  const { paletteKey: palette, setPaletteOverride } = usePaletteControl();
 
   const [password,    setPassword]    = useState('');
   const [connecting,  setConnecting]  = useState(false);
@@ -225,10 +225,7 @@ export default function SettingsScreen() {
                 active={palette === key}
                 accent={keyAccent}
                 dim={keyDim}
-                onPress={() => {
-                  setPalette(key);
-                  setSetting(db, 'palette_override', key);
-                }}
+                onPress={() => setPaletteOverride(key)}
               />
             );
           })}

mobile/app/_layout.tsx

@@ -2,12 +2,15 @@ import { Stack } from 'expo-router';
 import { SQLiteProvider } from 'expo-sqlite';
 import { StatusBar } from 'expo-status-bar';
 import { migrateDb } from '@/db';
+import { ThemeProvider } from '@/ThemeContext';
 
 export default function RootLayout() {
   return (
     <SQLiteProvider databaseName="bincio.db" onInit={migrateDb}>
+      <ThemeProvider>
         <StatusBar style="light" />
         <Stack screenOptions={{ headerShown: false }} />
+      </ThemeProvider>
     </SQLiteProvider>
   );
 }

mobile/theme.ts

@@ -1,5 +1,3 @@
-import { useSetting } from '@/db/queries';
-
 export type PaletteKey = 'auto' | 'default' | 'giro' | 'tour' | 'vuelta';
 
 export const PALETTES = {
@@ -29,8 +27,3 @@ export function autoKey(): Exclude<PaletteKey, 'auto'> {
   return 'default';
 }
 
-export function useTheme(): Theme {
-  const override = (useSetting('palette_override') ?? 'auto') as PaletteKey;
-  const key = override === 'auto' ? autoKey() : override;
-  return PALETTES[key as keyof typeof PALETTES] ?? PALETTES.default;
-}