chore: add flathub submission (janhq#4391)

ai.menlo.jan.desktop

@@ -0,0 +1,9 @@
+[Desktop Entry]
+Name=Jan
+Comment=Local AI Assistant that runs 100% offline
+Exec=run.sh
+Icon=ai.menlo.jan
+Type=Application
+Categories=Development;
+Keywords=AI;Assistant;LLM;ChatGPT;Local;Offline;
+StartupNotify=true

ai.menlo.jan.metainfo.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<component type="desktop-application">
+  <id>ai.menlo.jan</id>
+  <metadata_license>FSFAP</metadata_license>
+  <project_license>AGPL-3.0-only</project_license>
+  <name>Jan</name>
+  <summary>Local AI Assistant that runs 100% offline on your device</summary>
+
+  <description>
+    <p>
+      Jan is a ChatGPT-alternative that runs 100% offline on your device. Our goal is to make it easy for anyone to download and run LLMs and use AI with full control and privacy.
+    </p>
+    <p>Features:</p>
+    <ul>
+      <li>Model Library with popular LLMs like Llama, Gemma, Mistral, or Qwen</li>
+      <li>Connect to Remote AI APIs like Groq and OpenRouter</li>
+      <li>Local API Server with OpenAI-equivalent API</li>
+      <li>Extensions for customizing Jan</li>
+    </ul>
+  </description>
+
+  <launchable type="desktop-id">ai.menlo.jan.desktop</launchable>
+
+  <screenshots>
+    <screenshot type="default">
+      <image>https://catalog.jan.ai/flatpak/demo.gif</image>
+    </screenshot>
+  </screenshots>
+
+  <url type="homepage">https://jan.ai/</url>
+  <url type="bugtracker">https://github.com/janhq/jan/issues</url>
+
+  <content_rating type="oars-1.1" />
+
+  <releases>
+    <release version="0.5.12" date="2024-01-02">
+      <description>
+        <p>Latest stable release of Jan AI</p>
+      </description>
+    </release>
+  </releases>
+</component>