KTailctl v0.21.5

No user-facing changes, only internal dependency updates.

Chores

Flatpak:

• Drop kiriagmi-addons dependency as it is now included in the platform/SDK

Go:

• Update golang.org/x/net from v0.47.0 to v0.49.0
• Update tailscale.com from v1.90.9 to v1.92.5
• Update go from 1.25.4 to 1.25.6

Python:

• Update jinja 3.1.5 to 3.1.6 (only used for internal development)