feat: Enhance task access control and session management

- Implemented API and web task access assertions in the task status polling endpoint.
- Added functions to remember and check task access in user sessions.
- Updated task status tests to validate access control based on session data.
- Enhanced download route tests to ensure proper access checks.
- Improved SEO metadata handling with dynamic social preview images.
- Updated sitemap generation to include blog posts and new tools.
- Added a social preview SVG for better sharing on social media platforms.

frontend/index.html

@@ -12,12 +12,16 @@
     <meta property="og:title" content="Dociva — Free Online File Tools" />
     <meta property="og:description" content="30+ free tools: merge, split, compress, convert PDFs, images, videos & text. No signup required." />
     <meta property="og:site_name" content="Dociva" />
+    <meta property="og:image" content="/social-preview.svg" />
+    <meta property="og:image:alt" content="Dociva social preview" />
     <meta property="og:locale" content="en_US" />
     <meta property="og:locale:alternate" content="ar_SA" />
     <meta property="og:locale:alternate" content="fr_FR" />
     <meta name="twitter:card" content="summary_large_image" />
     <meta name="twitter:title" content="Dociva — Free Online File Tools" />
     <meta name="twitter:description" content="30+ free tools: merge, split, compress, convert PDFs, images, videos & text. No signup required." />
+    <meta name="twitter:image" content="/social-preview.svg" />
+    <meta name="twitter:image:alt" content="Dociva social preview" />
     <link rel="dns-prefetch" href="https://fonts.googleapis.com" />
     <link rel="dns-prefetch" href="https://fonts.gstatic.com" />
     <link rel="preconnect" href="https://fonts.googleapis.com" />