feat: add Android/Capacitor platform support via overlay system

- Add Android project (Capacitor-generated, app ID com.paarrot.app)
- Add capacitor.config.json at repo root (webDir: cinny/dist)
- Add overlay/ directory with mobile-specific source patches:
  - tauri.ts: Capacitor native detection, LocalNotifications, permission APIs
  - matrix.ts / useAuthenticatedMediaUrl.ts: legacy /_matrix/media/ URL support
  - SystemNotification.tsx: Capacitor permission request flow
  - ClientNonUIFeatures.tsx: Capacitor notification routing
  - tsconfig.json: moduleResolution bundler, rootDir set
  - package-additions.json: @capacitor/* deps to merge at build time
- Add scripts/apply-overlay.mjs: applies overlay onto clean cinny submodule before build
- Update android:prepare script to run apply-overlay before build + cap sync

overlay/src/app/features/settings/notifications/SystemNotification.tsx

@@ -0,0 +1,160 @@
+import React, { useCallback } from 'react';
+import { Box, Text, Switch, Button, color, Spinner } from 'folds';
+import { IPusherRequest } from 'matrix-js-sdk';
+import { SequenceCard } from '../../../components/sequence-card';
+import { SequenceCardStyle } from '../styles.css';
+import { SettingTile } from '../../../components/setting-tile';
+import { useSetting } from '../../../state/hooks/settings';
+import { settingsAtom } from '../../../state/settings';
+import { getNotificationState, usePermissionState } from '../../../hooks/usePermission';
+import { useEmailNotifications } from '../../../hooks/useEmailNotifications';
+import { AsyncStatus, useAsyncCallback } from '../../../hooks/useAsyncCallback';
+import { useMatrixClient } from '../../../hooks/useMatrixClient';
+import { isCapacitorNative, requestSystemNotificationPermission } from '../../../utils/tauri';
+
+function EmailNotification() {
+  const mx = useMatrixClient();
+  const [result, refreshResult] = useEmailNotifications();
+
+  const [setState, setEnable] = useAsyncCallback(
+    useCallback(
+      async (email: string, enable: boolean) => {
+        if (enable) {
+          await mx.setPusher({
+            kind: 'email',
+            app_id: 'm.email',
+            pushkey: email,
+            app_display_name: 'Email Notifications',
+            device_display_name: email,
+            lang: 'en',
+            data: {
+              brand: 'Paarrot',
+            },
+            append: true,
+          });
+          return;
+        }
+        await mx.setPusher({
+          pushkey: email,
+          app_id: 'm.email',
+          kind: null,
+        } as unknown as IPusherRequest);
+      },
+      [mx]
+    )
+  );
+
+  const handleChange = (value: boolean) => {
+    if (result && result.email) {
+      setEnable(result.email, value).then(() => {
+        refreshResult();
+      });
+    }
+  };
+
+  return (
+    <SettingTile
+      title="Email Notification"
+      description={
+        <>
+          {result && !result.email && (
+            <Text as="span" style={{ color: color.Critical.Main }} size="T200">
+              Your account does not have any email attached.
+            </Text>
+          )}
+          {result && result.email && <>Send notification to your email. {`("${result.email}")`}</>}
+          {result === null && (
+            <Text as="span" style={{ color: color.Critical.Main }} size="T200">
+              Unexpected Error!
+            </Text>
+          )}
+          {result === undefined && 'Send notification to your email.'}
+        </>
+      }
+      after={
+        <>
+          {setState.status !== AsyncStatus.Loading &&
+            typeof result === 'object' &&
+            result?.email && <Switch value={result.enabled} onChange={handleChange} />}
+          {(setState.status === AsyncStatus.Loading || result === undefined) && (
+            <Spinner variant="Secondary" />
+          )}
+        </>
+      }
+    />
+  );
+}
+
+export function SystemNotification() {
+  const notifPermission = usePermissionState('notifications', getNotificationState());
+  const capacitorNative = isCapacitorNative();
+  const [showNotifications, setShowNotifications] = useSetting(settingsAtom, 'showNotifications');
+  const [isNotificationSounds, setIsNotificationSounds] = useSetting(
+    settingsAtom,
+    'isNotificationSounds'
+  );
+
+  const requestNotificationPermission = async () => {
+    await requestSystemNotificationPermission();
+  };
+
+  return (
+    <Box direction="Column" gap="100">
+      <Text size="L400">System</Text>
+      <SequenceCard
+        className={SequenceCardStyle}
+        variant="SurfaceVariant"
+        direction="Column"
+        gap="400"
+      >
+        <SettingTile
+          title="Desktop Notifications"
+          description={
+            notifPermission === 'denied' ? (
+              <Text as="span" style={{ color: color.Critical.Main }} size="T200">
+                {'Notification' in window
+                  ? 'Notification permission is blocked. Please allow notification permission from browser address bar.'
+                  : 'Notifications are not supported by the system.'}
+              </Text>
+            ) : (
+              <span>Show desktop notifications when message arrive.</span>
+            )
+          }
+          after={
+            notifPermission === 'prompt' ? (
+              <Button size="300" radii="300" onClick={requestNotificationPermission}>
+                <Text size="B300">Enable</Text>
+              </Button>
+            ) : (
+              <Switch
+                disabled={!capacitorNative && notifPermission !== 'granted'}
+                value={showNotifications}
+                onChange={setShowNotifications}
+              />
+            )
+          }
+        />
+      </SequenceCard>
+      <SequenceCard
+        className={SequenceCardStyle}
+        variant="SurfaceVariant"
+        direction="Column"
+        gap="400"
+      >
+        <SettingTile
+          title="Notification Sound"
+          description="Play sound when new message arrive."
+          after={<Switch value={isNotificationSounds} onChange={setIsNotificationSounds} />}
+        />
+      </SequenceCard>
+      <SequenceCard
+        className={SequenceCardStyle}
+        variant="SurfaceVariant"
+        direction="Column"
+        gap="400"
+      >
+        <EmailNotification />
+      </SequenceCard>
+    </Box>
+  );
+}