feat(mobile): Add support for viewing PDFs (#1519)

* feat(mobile): add react-native-pdf dependency

Add react-native-pdf package to enable PDF viewing functionality
in the mobile app. This will be used to display PDF bookmarks
directly within the app.

Part of #597

🤖 Generated with [Claude Code](https://claude.ai/code)

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

* feat(mobile): add PDF viewer component with authentication support

Add a dedicated PDFViewer component that handles downloading and
displaying PDF assets with proper authentication headers. Features
include:

- Download progress indication
- Error handling with user-friendly messages
- Automatic cleanup of temporary files
- Proper memory management to prevent leaks
- Content type validation for PDF files

Part of #597

🤖 Generated with [Claude Code](https://claude.ai/code)

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

* feat(mobile): integrate PDF viewing in bookmark detail view

Integrate the PDFViewer component to display PDF bookmarks inline.
When a bookmark is a PDF asset, it now renders using the dedicated
PDF viewer instead of treating it as an image.

Also adds external PDF opening functionality with platform-specific
handling for iOS and Android, proper filename handling, and temporary
file cleanup.

Additionally fixes dark mode styling for the navigation header to ensure
proper contrast in both light and dark themes.

Part of #597

🤖 Generated with [Claude Code](https://claude.ai/code)

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

* revert the open externally button

* use react query for downloading the pdf

---------

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: MohamedBassem <me@mbassem.com>

1 files changed, 135 insertions, 0 deletions

diff --git a/apps/mobile/components/bookmarks/PDFViewer.tsx b/apps/mobile/components/bookmarks/PDFViewer.tsx
new file mode 100644
index 00000000..24b9edfb
--- /dev/null
+++ b/apps/mobile/components/bookmarks/PDFViewer.tsx
@@ -0,0 +1,135 @@
+import React, { useEffect, useMemo, useState } from "react";
+import { ActivityIndicator, StyleSheet, Text, View } from "react-native";
+import ReactNativeBlobUtil from "react-native-blob-util";
+import Pdf from "react-native-pdf";
+import { useQuery } from "@tanstack/react-query";
+import { useColorScheme } from "nativewind";
+
+interface PDFViewerProps {
+  source: string;
+  headers?: Record<string, string>;
+}
+
+export function PDFViewer({ source, headers }: PDFViewerProps) {
+  const [pdfRenderError, setPdfRenderError] = useState<string | null>(null);
+  const { colorScheme } = useColorScheme();
+  const isDark = colorScheme === "dark";
+  const colors = {
+    background: isDark ? "#000" : "#fff",
+    foreground: isDark ? "#fff" : "#000",
+    mutedForeground: isDark ? "#888" : "#666",
+  };
+
+  const {
+    data: localPath,
+    isLoading,
+    error: downloadError,
+  } = useQuery({
+    queryKey: ["pdf", source],
+    queryFn: async () => {
+      // Create a temporary filename
+      const fileName = `temp_${Date.now()}.pdf`;
+      const { dirs } = ReactNativeBlobUtil.fs;
+      const path = `${dirs.DocumentDir}/${fileName}`;
+
+      const response = await ReactNativeBlobUtil.config({
+        fileCache: true,
+        path,
+      }).fetch("GET", source, headers ?? {});
+      return response.path();
+    },
+    enabled: !!source,
+  });
+
+  // Merge download and render errors
+  const error = useMemo(() => {
+    if (downloadError) {
+      let errorMessage = "Failed to download PDF";
+      if (downloadError.message.includes("Network request failed")) {
+        errorMessage = "Network error. Please check your connection.";
+      } else if (
+        downloadError.message.includes("401") ||
+        downloadError.message.includes("403")
+      ) {
+        errorMessage = "Authentication failed. Please sign in again.";
+      } else if (downloadError.message.includes("404")) {
+        errorMessage = "PDF not found.";
+      }
+      return errorMessage;
+    }
+    if (pdfRenderError) {
+      return pdfRenderError;
+    }
+    return null;
+  }, [downloadError, pdfRenderError]);
+
+  // Cleanup function to remove temporary file on unmount
+  useEffect(() => {
+    return () => {
+      if (localPath) {
+        ReactNativeBlobUtil.fs.unlink(localPath).catch(() => ({}));
+      }
+    };
+  }, [source, headers]);
+
+  if (error) {
+    return (
+      <View style={[styles.container, { backgroundColor: colors.background }]}>
+        <Text style={[styles.errorText, { color: colors.foreground }]}>
+          {error}
+        </Text>
+      </View>
+    );
+  }
+
+  if (isLoading || !localPath) {
+    return (
+      <View style={[styles.container, { backgroundColor: colors.background }]}>
+        <View style={styles.loadingContainer}>
+          <ActivityIndicator size="large" color={colors.foreground} />
+          <Text style={[styles.loadingText, { color: colors.mutedForeground }]}>
+            Downloading PDF...
+          </Text>
+        </View>
+      </View>
+    );
+  }
+
+  return (
+    <View style={[styles.container, { backgroundColor: colors.background }]}>
+      <Pdf
+        style={StyleSheet.absoluteFillObject}
+        source={{ uri: `file://${localPath}`, cache: true }}
+        spacing={16}
+        maxScale={3}
+        onLoadComplete={() => ({})}
+        onError={() => setPdfRenderError("Failed to render PDF")}
+        trustAllCerts={false}
+        renderActivityIndicator={() => (
+          <ActivityIndicator size="large" color={colors.foreground} />
+        )}
+      />
+    </View>
+  );
+}
+
+const styles = StyleSheet.create({
+  container: {
+    flex: 1,
+  },
+  loadingContainer: {
+    ...StyleSheet.absoluteFillObject,
+    justifyContent: "center",
+    alignItems: "center",
+    zIndex: 1,
+  },
+  loadingText: {
+    marginTop: 12,
+    fontSize: 16,
+  },
+  errorText: {
+    fontSize: 16,
+    textAlign: "center",
+    padding: 20,
+  },
+});