DNS single-source Phase 1 + decommission Tailscale fleet-wide

Phase 1 of the DNS-redundancy cleanup (keep NetBird, collapse toward one
zone) — the safe, mesh-independent half:

- Every homelab LXC now resolves via Technitium (192.168.8.2). Fixed 8
  boxes on a dead resolver (.180), the router (.1), or Tailscale MagicDNS
  (100.100.100.100): 101,102,104,105,106,114,119,126.
- Removed the redundant /etc/hosts auth/mcp/secrets overrides (Technitium
  returns identical-or-better answers); disabled hubris-hosts-override.
- Net effect: on-prem DNS (LXCs + household via Fritz!Box->Technitium) is
  now NetBird-independent, so dropping the managed zone later can't break
  on-LAN resolution. Phases 2-4 still pending.

Tailscale decommissioned (was legacy/being-phased-out):
- Removed from the 6 LXCs still running it (101,103,104,105,114,119):
  logout, disable tailscaled, apt purge, state cleared.
- inventory.yaml: dropped tailscale from accepted + all mesh blocks;
  regenerated hosts/*.yaml (also pruned orphan authentik/claudio-bot).
- Tightened secrets-issuance MESH_SUBNETS: removed the now-vestigial
  Tailscale CGNAT range 100.64.0.0/10.
- Updated narrative docs (mesh, dns, network, README, AGENTS,
  agent-enrollment, homelab-context, 105-apps, 107-dns).

Live infra changed on the fleet + Mac; this commit records the docs/inventory.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

containers/105-apps.md

@@ -87,9 +87,10 @@ same key. Mesh+LAN source-IP gated via the `MESH_SUBNETS` env in
 - `/revoke` is admin-token-gated by `/etc/secrets-issuance/admin-token`;
   shreds the local key file and adds the hostname to the denylist.
   Called by `homelab client remove`.
-- Trust subnets today: `100.122.0.0/16` (Netbird), `100.64.0.0/10`
-  (Tailscale), `192.168.8.0/24` (LAN). Tighten if the LAN gets
-  untrusted devices.
+- Trust subnets today: `100.122.0.0/16` (Netbird), `192.168.8.0/24` (LAN).
+  (The legacy Tailscale CGNAT range `100.64.0.0/10` was removed from
+  `secrets-issuance`'s `MESH_SUBNETS` on 2026-06-21 when Tailscale was
+  decommissioned; service restarted.) Tighten if the LAN gets untrusted devices.
 
 #### Auto-deploy pipeline (secrets-issuance)
 Receiver at `/opt/secrets-issuance/secrets-issuance/deploy/webhook/`,