feat(packaging): add standalone Flathub manifest and bundle icon (#1060)

docs/packaging.md

@@ -87,7 +87,7 @@ custom TLS stores) may need extra permissions, e.g.:
 flatpak override --user com.queryahub.querya_desktop --filesystem=/var/run/postgresql:ro
 ```
 
-Flathub submission can reuse [`packaging/linux/flatpak/com.queryahub.querya_desktop.yml`](../packaging/linux/flatpak/com.queryahub.querya_desktop.yml).
+Flathub submission uses [`packaging/linux/flatpak/com.queryahub.querya_desktop.flathub.yml`](../packaging/linux/flatpak/com.queryahub.querya_desktop.flathub.yml) (downloads release zip with checksum), while local build script uses [`packaging/linux/flatpak/com.queryahub.querya_desktop.yml`](../packaging/linux/flatpak/com.queryahub.querya_desktop.yml).
 
 ## APT and DNF repository (`repo.querya.app`)
 

packaging/linux/flatpak/com.queryahub.querya_desktop.flathub.yml

@@ -0,0 +1,36 @@
+app-id: com.queryahub.querya_desktop
+runtime: org.gnome.Platform
+runtime-version: '48'
+sdk: org.gnome.Sdk
+command: querya_desktop
+
+finish-args:
+  - --share=network
+  - --share=ipc
+  - --socket=fallback-x11
+  - --socket=wayland
+  - --device=dri
+  - --filesystem=home
+  - --talk-name=org.freedesktop.secrets
+
+modules:
+  - name: querya-desktop
+    buildsystem: simple
+    build-commands:
+      - install -Dm755 querya_desktop /app/bin/querya_desktop
+      - cp -a lib /app/
+      - cp -a data /app/
+      - install -Dm644 com.queryahub.querya_desktop.desktop /app/share/applications/com.queryahub.querya_desktop.desktop
+      - install -Dm644 com.queryahub.querya_desktop.png /app/share/icons/hicolor/512x512/apps/com.queryahub.querya_desktop.png
+      - install -Dm644 com.queryahub.querya_desktop.metainfo.xml /app/share/metainfo/com.queryahub.querya_desktop.metainfo.xml
+    sources:
+      - type: archive
+        url: https://github.com/QueryaHub/Querya-Desktop/releases/download/0.4.18/Querya-Desktop-0.4.18-linux.zip
+        sha256: cf840e11f47309b416c46fbfeb0230f099441ac66037b425a935c5ef3687aba2
+        strip-components: 0
+      - type: file
+        path: com.queryahub.querya_desktop.desktop
+      - type: file
+        path: com.queryahub.querya_desktop.metainfo.xml
+      - type: file
+        path: com.queryahub.querya_desktop.png