Add flatpak build job to CI

diff --git a/.github/workflows/build.yaml b/.github/workflows/build.yaml
index e9dd3ed..6a92ed6 100644
--- a/.github/workflows/build.yaml
+++ b/.github/workflows/build.yaml
@@ -484,9 +484,75 @@ jobs:
           name: stack_wallet-ios-aarch64-${{ steps.ver.outputs.version }}
           path: stack_wallet-ios-aarch64-${{ steps.ver.outputs.version }}.ipa
 
+  build-flatpak:
+    runs-on: ubuntu-24.04
+    needs: build-linux
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Set version
+        id: ver
+        run: |
+          if [ "${{ github.ref_type }}" = "tag" ]; then
+            VERSION="${{ github.ref_name }}"
+            VERSION="${VERSION#v}"
+          elif [ -n "${{ inputs.version }}" ]; then
+            VERSION="${{ inputs.version }}"
+          else
+            VERSION="0.0.0-staging.${{ github.run_number }}"
+          fi
+          echo "version=${VERSION}" >> $GITHUB_OUTPUT
+
+      - name: Download Linux bundle
+        uses: actions/download-artifact@v4
+        with:
+          name: stack_wallet-linux-x86_64-${{ steps.ver.outputs.version }}
+
+      - name: Stage bundle and icon
+        run: |
+          tar -xzf "stack_wallet-linux-x86_64-${{ steps.ver.outputs.version }}.tar.gz" -C flatpak/
+          cp asset_sources/icon/stack_wallet/icon.png flatpak/com.cypherstack.stackwallet.png
+
+      - name: Install Flatpak tools
+        run: |
+          sudo apt-get update -q
+          sudo apt-get install -y flatpak flatpak-builder
+
+      - name: Set up Flathub remote
+        run: flatpak remote-add --user --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo
+
+      - name: Cache Flatpak SDK
+        uses: actions/cache@v4
+        with:
+          path: ~/.local/share/flatpak
+          key: flatpak-freedesktop-24.08-v1
+
+      - name: Install Flatpak SDK
+        run: |
+          flatpak install --user --noninteractive flathub \
+            org.freedesktop.Platform//24.08 \
+            org.freedesktop.Sdk//24.08
+
+      - name: Build Flatpak
+        run: |
+          flatpak-builder --user --force-clean \
+            --repo=flatpak-repo \
+            build-flatpak flatpak/com.cypherstack.stackwallet.yaml
+
+      - name: Bundle Flatpak
+        run: |
+          flatpak build-bundle flatpak-repo \
+            "stack_wallet-linux-x86_64-${{ steps.ver.outputs.version }}.flatpak" \
+            com.cypherstack.stackwallet
+
+      - uses: actions/upload-artifact@v4
+        with:
+          name: stack_wallet-flatpak-x86_64-${{ steps.ver.outputs.version }}
+          path: stack_wallet-linux-x86_64-${{ steps.ver.outputs.version }}.flatpak
+
   release:
     if: github.ref_type == 'tag'
-    needs: [build-linux, build-android, build-windows, build-macos, build-ios]
+    needs: [build-linux, build-android, build-windows, build-macos, build-ios, build-flatpak]
     runs-on: ubuntu-latest
     permissions:
       contents: write
@@ -503,7 +569,7 @@ jobs:
             name=$(basename "$dir")
             (cd "$dir" && zip -r "../../release-files/${name}.zip" .)
           done
-          find artifacts/ \( -name "*.tar.gz" -o -name "*.zip" -o -name "*.ipa" \) -mindepth 2 -exec mv {} release-files/ \;
+          find artifacts/ \( -name "*.tar.gz" -o -name "*.zip" -o -name "*.ipa" -o -name "*.flatpak" \) -mindepth 2 -exec mv {} release-files/ \;
           find artifacts/ -name "*.apk" -mindepth 2 -exec mv {} release-files/ \;
 
       - uses: softprops/action-gh-release@v2
diff --git a/flatpak/com.cypherstack.stackwallet.desktop b/flatpak/com.cypherstack.stackwallet.desktop
new file mode 100644
index 0000000..d5b7d55
--- /dev/null
+++ b/flatpak/com.cypherstack.stackwallet.desktop
@@ -0,0 +1,7 @@
+[Desktop Entry]
+Name=Stack Wallet
+Comment=Open-source non-custodial cryptocurrency wallet
+Exec=stack_wallet
+Icon=com.cypherstack.stackwallet
+Type=Application
+Categories=Finance;
diff --git a/flatpak/com.cypherstack.stackwallet.metainfo.xml b/flatpak/com.cypherstack.stackwallet.metainfo.xml
new file mode 100644
index 0000000..abf3b19
--- /dev/null
+++ b/flatpak/com.cypherstack.stackwallet.metainfo.xml
@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<component type="desktop-application">
+  <id>com.cypherstack.stackwallet</id>
+  <metadata_license>CC0-1.0</metadata_license>
+  <project_license>GPL-3.0-only</project_license>
+  <name>Stack Wallet</name>
+  <summary>Open-source non-custodial cryptocurrency wallet</summary>
+  <description>
+    <p>
+      Stack Wallet is an open-source, non-custodial, privacy-focused
+      cryptocurrency wallet supporting multiple coins.
+    </p>
+  </description>
+  <url type="homepage">https://stackwallet.com</url>
+  <url type="bugtracker">https://github.com/cypherstack/stack_wallet/issues</url>
+  <content_rating type="oars-1.1"/>
+</component>
diff --git a/flatpak/com.cypherstack.stackwallet.yaml b/flatpak/com.cypherstack.stackwallet.yaml
new file mode 100644
index 0000000..3707ccb
--- /dev/null
+++ b/flatpak/com.cypherstack.stackwallet.yaml
@@ -0,0 +1,35 @@
+app-id: com.cypherstack.stackwallet
+runtime: org.freedesktop.Platform
+runtime-version: '24.08'
+sdk: org.freedesktop.Sdk
+command: stack_wallet
+
+finish-args:
+  - --share=network
+  - --share=ipc
+  - --socket=fallback-x11
+  - --socket=wayland
+  - --device=dri
+  - --talk-name=org.freedesktop.secrets
+  - --talk-name=org.freedesktop.Notifications
+
+modules:
+  - name: stack_wallet
+    buildsystem: simple
+    build-commands:
+      # Install the pre-built Flutter bundle under /app/lib/stack_wallet/ so
+      # the binary's $ORIGIN/lib and $ORIGIN/data lookups resolve correctly.
+      - mkdir -p /app/lib/stack_wallet
+      - install -Dm755 bundle/stack_wallet /app/lib/stack_wallet/stack_wallet
+      - cp -r bundle/lib bundle/data /app/lib/stack_wallet/
+      # Wrapper script so the Flatpak command path resolves to the binary.
+      - install -Dm755 stack_wallet.sh /app/bin/stack_wallet
+      - install -Dm644 com.cypherstack.stackwallet.desktop
+          /app/share/applications/com.cypherstack.stackwallet.desktop
+      - install -Dm644 com.cypherstack.stackwallet.metainfo.xml
+          /app/share/metainfo/com.cypherstack.stackwallet.metainfo.xml
+      - install -Dm644 com.cypherstack.stackwallet.png
+          /app/share/icons/hicolor/512x512/apps/com.cypherstack.stackwallet.png
+    sources:
+      - type: dir
+        path: .
diff --git a/flatpak/stack_wallet.sh b/flatpak/stack_wallet.sh
new file mode 100644
index 0000000..db2f325
--- /dev/null
+++ b/flatpak/stack_wallet.sh
@@ -0,0 +1,2 @@
+#!/bin/sh
+exec /app/lib/stack_wallet/stack_wallet "$@"