fix: NetworkManager DNS conflicts with systemd-resolved

[arafays]

I installed network manager while installing arch and was running into problem that i was unable to browse internet until i ran the setup dns script in omarchy this fixes it perminently updates the network manger and patches it configuration.

This pull request adds a migration script to address DNS conflicts between NetworkManager and systemd-resolved. The script checks for misconfigurations and hardcoded DNS entries, applies necessary fixes, and restarts NetworkManager if changes are made.

NetworkManager and systemd-resolved DNS integration:

• Added migrations/1757005778.sh to detect and fix DNS configuration conflicts between NetworkManager and systemd-resolved, ensuring proper integration.
• Checks for the presence and status of NetworkManager and systemd-resolved before proceeding with configuration changes.
• Detects missing or incorrect NetworkManager DNS configuration in /etc/NetworkManager/conf.d/99-dns-systemd-resolved.conf and creates or updates the file as needed.
• Identifies NetworkManager connections with hardcoded DNS settings and clears them to prevent conflicts.
• Restarts NetworkManager automatically if any DNS configuration changes are applied.This migration ensures NetworkManager and systemd-resolved cooperate by:
  • Enforcing dns=systemd-resolved in a dedicated NetworkManager conf.
  • Detecting and clearing hardcoded IPv4 DNS on active connections.
  • Restarting NetworkManager when changes are applied.

The goal is to prevent DNS resolution conflicts and flaky name lookups on systems using systemd-resolved alongside NetworkManager.

[jardahrazdera]

Omarchy doesn't use NetworkManager. We use systemd-networkd + iwd by design.

This migration would be a no-op on standard Omarchy systems.

cc @dhh

See #1446 for context.