Update BorgBase repo ID after recreation (#144)

## Summary
- Previous BorgBase repo (k04ljcd7) had corrupted segments from interrupted backup attempts
- Recreated as u3ugi1x1 (same US region, same SSH key, same append-only settings)
- Updates repo path in Ansible defaults and known_hosts hostname in tasks

## Post-merge
1. `mise run provision-indri -- --tags borgmatic`
2. `ssh indri 'mise x -- borgmatic init --encryption repokey --repository borgbase-offsite'`
3. `mise x -- borgmatic create --repository borgbase-offsite --verbosity 1 --progress`

Reviewed-on: https://forge.ops.eblu.me/eblume/blumeops/pulls/144

ansible/roles/borgmatic/tasks/main.yml

@@ -29,8 +29,8 @@
 
 - name: Add BorgBase host key to known_hosts
   ansible.builtin.known_hosts:
-    name: k04ljcd7.repo.borgbase.com
-    key: "k04ljcd7.repo.borgbase.com ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIGU0mISTyHBw9tBs6SuhSq8tvNM8m9eifQxM+88TowPO"
+    name: u3ugi1x1.repo.borgbase.com
+    key: "u3ugi1x1.repo.borgbase.com ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIGU0mISTyHBw9tBs6SuhSq8tvNM8m9eifQxM+88TowPO"
     state: present
 
 - name: Deploy borgmatic configuration