Upgrade OS --> 26.04

[enoch85]

Summary

• Bump supported Ubuntu range to 24.04 → 26.04 LTS (Resolute Raccoon)
• Update defaults: PHP 8.5, PostgreSQL 18, kernel 7.0
• Centralize all OS-version checks in lib.sh (SUPPORTED_VERSION_MIN/MAX, LATEST_VERSION derived, SUPPORTED_CODENAMES) so the next bump is a 3-line edit
• Make check_php() fully dynamic (regex on php -v, /etc/php fallback)
• Replace hardcoded stop_if_installed lists with brace-expansion loops
• Drop python2 from apps/webmin.sh (no install candidate on 26.04, no longer required by Webmin)

External source / dependency audit

Source	Where	Behavior on 26.04	Action
Webmin	apps/webmin.sh	Uses sarge contrib suite — codename-independent. Works on any Debian/Ubuntu	✅ none
morph027/coturn	apps/talk.sh:137	Gated to ${CODENAME} == "jammy" only — already no-op on noble/resolute. coturn is then installed from Ubuntu's own repo	✅ none (same as 24.04 PR)
morph027/janus	apps/talk.sh:351	Case-gated to bionic|focal — no-op on resolute. janus from Ubuntu's own repo	✅ none (same as 24.04 PR)
morph027/nats-server	apps/talk.sh:301	Suite nats main — codename-agnostic	⚠️ relies on upstream supporting resolute; verify on first Talk install
morph027/spreed-signaling	apps/talk.sh:374	Suite signaling main — codename-agnostic	⚠️ same caveat
PostgreSQL PGDG	migrate/docker/migrate.sh:56	Uses $(lsb_release -cs)-pgdg — auto-picks resolute-pgdg	⚠️ works only once PGDG publishes a resolute distro (typically within weeks of LTS release). Only used by the docker-migration helper, low traffic
MaxMind PPA	network/geoblock.sh:88	PPAs are per-codename	⚠️ works if Canonical/MaxMind rebuilt for resolute
Docker CE	lib.sh:1902 (get.docker.com)	Universal install script — Docker tracks new LTS quickly	✅ none
Netdata	apps/netdata.sh:66 (get.netdata.cloud)	Universal install script	✅ none
MaxMind mod_maxminddb	network/geoblock.sh:107	Pinned tarball v1.2.0 built from source	✅ none
Snap (certbot, bpytop)	lib.sh, apps/bpytop.sh	Snaps are distro-agnostic	✅ none
Webmin .deb fallback	apps/webmin.sh:85	Pinned webmin_2.010_all.deb (sourceforge) — distro-agnostic	✅ none
python2	apps/webmin.sh:55	Not installable on 26.04	🛠️ removed
ImageMagick 6	apps/imaginary.sh:82	IM6 packages removed from 26.04 — but only used in is_this_installed removal guard, skipped on fresh installs	✅ none
PostgreSQL 18 default	apt postgresql meta-package	Confirmed shipping on 26.04	✅ matches README bump
Redis 8.0 default	apt redis-server	New major (was 7.x on 24.04) — config syntax compatible with our requirepass + unix socket setup	✅ none
ZFS 2.4 default	apt zfsutils-linux	New minor (was 2.2 on 24.04) — backward compatible	✅ none

Test plan

• bash -n on all 17 modified scripts
• shellcheck (repo CI flags) — zero warnings
• Sourced lib.sh in real Ubuntu 26.04 container — variables resolve, version()/check_distro_version()/check_php() pass positive and negative tests
• Confirmed PG 18, PHP 8.5, Redis 8.0 are the defaults on 26.04
• Confirmed python2 not installable on 26.04 → fix included
• Full install run on a fresh 26.04 VM
• Talk install end-to-end (verifies morph027 nats-server + spreed-signaling upstream availability)
• GeoBlock install (verifies MaxMind PPA on resolute)