Snapshot 49.0 release

• Make app DBus-activatable
• Improve how GstCaps were created
• Support for hardware video encoding
• Prefer H264/MP4 format if possible fore recording
• Use native GTK's YUV support if available
• Mirrored QR codes can now be scanned
• Remove video-format gsetting
• Port shortcuts dialog to AdwShortcutsDialog
• Remove meson option to run without portals
• Show release notes on about dialog
• Add warning when there are missing GStreamer plugins
• Updated translations