gui: add Wails v3 desktop app skeleton

- Go upgraded to 1.25.10 (required by Wails v3)
- Wails v3 installed (alpha.96)
- Frontend: Svelte+Vite scaffold in frontend/
- guimain.go: Wails GUI entry point (compiled with -tags gui)
- wails_service.go: stub service for Wails bindings
- Verstak desktop binary builds: go build -tags gui -o verstak-gui .
- CLI (./cmd/verstak/) unaffected
- Legacy HTTP GUI (internal/gui/) preserved as prototype
- Build: 24MB ELF binary with GTK4/WebKit2GTK-6

Build commands:
  CLI:  go build -o verstak ./cmd/verstak/
  GUI:  cd frontend && npm run build && go build -tags gui -o verstak-gui .

build/linux/nfpm/nfpm.yaml

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+# Feel free to remove those if you don't want/need to use them.
+# Make sure to check the documentation at https://nfpm.goreleaser.com
+#
+# The lines below are called `modelines`. See `:help modeline`
+
+name: "verstak"
+arch: ${GOARCH}
+platform: "linux"
+version: "0.1.0"
+section: "default"
+priority: "extra"
+maintainer: ${GIT_COMMITTER_NAME} <${GIT_COMMITTER_EMAIL}>
+description: "A verstak application"
+vendor: "My Company"
+homepage: "https://wails.io"
+license: "MIT"
+release: "1"
+
+contents:
+  - src: "./bin/verstak"
+    dst: "/usr/local/bin/verstak"
+  - src: "./build/appicon.png"
+    dst: "/usr/share/icons/hicolor/128x128/apps/verstak.png"
+  - src: "./build/linux/verstak.desktop"
+    dst: "/usr/share/applications/verstak.desktop"
+
+# Default dependencies for the GTK4 + WebKitGTK 6.0 stack (Ubuntu 24.04+ / Debian 13+)
+depends:
+  - libgtk-4-1
+  - libwebkitgtk-6.0-4
+
+# Distribution-specific overrides for different package formats
+overrides:
+  # RPM packages for Fedora / RHEL / AlmaLinux / Rocky Linux
+  rpm:
+    depends:
+      - gtk4
+      - webkitgtk6.0
+
+  # Arch Linux packages
+  archlinux:
+    depends:
+      - gtk4
+      - webkitgtk-6.0
+
+# scripts section to ensure desktop database is updated after install
+scripts:
+  postinstall: "./build/linux/nfpm/scripts/postinstall.sh"
+  # You can also add preremove, postremove if needed
+  # preremove: "./build/linux/nfpm/scripts/preremove.sh"
+  # postremove: "./build/linux/nfpm/scripts/postremove.sh"
+
+# If you build your app with -tags gtk3 (legacy WebKit2GTK 4.1 stack — supported through v3.0.x, removed in v3.1),
+# replace the depends/overrides above with these:
+#
+# depends:
+#   - libgtk-3-0
+#   - libwebkit2gtk-4.1-0
+# overrides:
+#   rpm:
+#     depends:
+#       - gtk3
+#       - webkit2gtk4.1
+#   archlinux:
+#     depends:
+#       - gtk3
+#       - webkit2gtk-4.1
+#
+# replaces:
+#   - foobar
+# provides:
+#   - bar
+# recommends:
+#   - whatever
+# suggests:
+#   - something-else
+# conflicts:
+#   - not-foo
+#   - not-bar
+# changelog: "changelog.yaml"

build/linux/nfpm/scripts/postinstall.sh

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+#!/bin/sh
+
+# Update desktop database for .desktop file changes
+# This makes the application appear in application menus and registers its capabilities.
+if command -v update-desktop-database >/dev/null 2>&1; then
+  echo "Updating desktop database..."
+  update-desktop-database -q /usr/share/applications
+else
+  echo "Warning: update-desktop-database command not found. Desktop file may not be immediately recognized." >&2
+fi
+
+# Update MIME database for custom URL schemes (x-scheme-handler)
+# This ensures the system knows how to handle your custom protocols.
+if command -v update-mime-database >/dev/null 2>&1; then
+  echo "Updating MIME database..."
+  update-mime-database -n /usr/share/mime
+else
+  echo "Warning: update-mime-database command not found. Custom URL schemes may not be immediately recognized." >&2
+fi
+
+exit 0

build/linux/nfpm/scripts/postremove.sh

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+#!/bin/bash

build/linux/nfpm/scripts/preinstall.sh

@@ -0,0 +1 @@
+#!/bin/bash

build/linux/nfpm/scripts/preremove.sh

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+#!/bin/bash