Declare all required dependencies in the Flatpak manifest

[TheZupZup]

Overview

Once the manifest exists (see #68), it needs to declare all dependencies so the app runs correctly inside the Flatpak sandbox.

Depends on: #68 (manifest) being created first.

What the app actually needs:

• Python 3 — available in GNOME SDK/Platform
• PyGObject (python3-gi) — available in GNOME Platform
• GTK 3 — available in GNOME Platform
• src/Qrip.ui (Glade XML file) — must be bundled alongside Qrip.py
• streamrip (rip CLI) — this is the hard part (see below)

The streamrip problem:
streamrip is a complex Python package with many dependencies. Options:

1. Bundle it inside the Flatpak (complex but self-contained)
2. Require it as a host prerequisite and document this clearly
3. Use --allow-talk-to=org.freedesktop.Flatpak to run the host's rip binary

What needs to be done

• Verify that python3-gi and GTK3 are already available in org.gnome.Platform (they are — just needs confirming)
• Decide and document how streamrip will be handled (bundle vs. prerequisite)
• Add any additional Python modules to the manifest if needed
• Ensure Qrip.ui is included in the build and placed where Qrip.py expects it

Goal

All required libraries are declared in the manifest and available at runtime inside the sandbox.

Related to: #30