Trim comments across configs and services

Shorten verbose multi-paragraph comments to essentials, and drop a
stale claim in common.nix that jupiter kept its own copy of the base
config (it now imports common.nix directly).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

services/seerr.nix

@@ -3,18 +3,11 @@
 # Seerr (formerly Jellyseerr) — request manager for Jellyfin, talks to
 # Sonarr/Radarr to fulfill requests. Fresh install, no migrated data.
 #
-# configDir is left at the module default (/var/lib/seerr) on purpose:
-# systemd's StateDirectory= auto-chown for DynamicUser only applies to that
-# exact default path, not to an arbitrary custom one (same class of issue as
-# prowlarr.nix, worked around the same way) — bind-mount AppData onto the
-# default path instead of overriding configDir, so it stays on the RAID array
-# and survives an OS-disk reinstall like every other service's data.
-#
-# Mount onto /var/lib/private/seerr, NOT the public /var/lib/seerr:
-# DynamicUser+StateDirectory keeps real data at .../private/<name> and makes
-# the public path a symlink to it; binding onto the public path turns it into
-# a mountpoint systemd then can't rename during its migrate-on-start dance
-# ("Device or resource busy", exit 238/STATE_DIRECTORY).
+# configDir stays at the module default; bind-mount AppData onto it instead
+# of overriding configDir, so data lives on the RAID array and survives an
+# OS-disk reinstall (same DynamicUser/StateDirectory issue as prowlarr.nix —
+# see that file for why, and why the mount targets /var/lib/private/seerr
+# rather than the public path).
 {
   services.seerr.enable = true;