fix(packaging): address code review findings

- Upgrade path restarts only fenris-collect.timer, not fenris-collect.service
  (spec §7: "a running oneshot finishes on its old interpreter")
- Remove redundant deb depends override in nfpm.yaml (top-level is sufficient)
- Remove common.sh sourcing — scripts are self-contained to avoid path
  dependency when dpkg/rpm run them from /var/lib/dpkg/info/

Co-authored-by: CommandCodeBot <noreply@commandcode.ai>

packaging/nfpm.yaml

@@ -47,12 +47,6 @@ scripts:
   postremove: packaging/postrm.sh
 
 overrides:
-  deb:
-    depends:
-      - python3 (>= 3.10)
-      - smartmontools
-      - systemd
-
   rpm:
     depends:
       - python3 >= 3.10