feat: +thin-client role + AZ-TC-01..03 pilot

Auf Basis des Grilling-Sessions mit 20 design decisions umgesetztes
v1-Skeleton der Thin-Client-Rolle plus 3 Pilot-Hosts.

Architektur:
- roles/thin-client/ als geschlossene Rolle (default.nix compose + 7
  Subdirectories: hardware, session, identity, network, peripherals,
  apps, monitoring, deployment)
- hosts/AZ-TC-NN/default.nix als ~20-Zeilen-Wrapper pro Fleet-Host
- flake.nix instanziiert AZ-TC-01..03 via Fleet-Helper
- secrets.nix mit per-host agenix-Secret-Stubs

Submodule:
- hardware: dell-optiplex-micro + generic-x86_64-uefi Fallback
- identity: AD (sssd/krb5/keytab via agenix), lokale Notfalluser
  (sascha.koenig + jannik.mueller ohne m3ta-home), sudo-Policy
- session: KDE Plasma 6 + Wayland + SDDM, Branding (Wallpaper + Footer),
  PipeWire Audio
- network: NetworkManager + wpa_supplicant + 802.1X EAP-TLS, NetBird
  + SSH via NetBird, systemd-resolved (Corp + NetBird DNS), hardened
  firewall, OpenSSH
- peripherals: CUPS mit Pull-Print-Queue, pam_mount für DFS-Shares
- apps: Chromium (ManagedBookmarks, Bitwarden force-install, no local
  passwords), Office-Web .desktop-Shortcuts, Remmina (mehrere TS,
  Kerberos SSO), RustDesk Client + Daemon, OBS Studio, Autostart
- monitoring: node_exporter → Pushgateway, Alloy (stub für Loki),
  Snipe-IT Asset-Checkin (stub)
- deployment: Disko BTRFS-Layout, auto-upgrade daily + reboot window,
  snapper snapshots

Build-Validierung: 'nix flake check' bestanden für AZ-TC-01/02/03.

Siehe roles/thin-client/README.md für den Provisionierungs-Workflow
und die Liste der noch auszufüllenden Platzhalter (TODO-Kommentare
in den jeweiligen Modulen).

roles/thin-client/identity/local-users.nix

@@ -0,0 +1,41 @@
+# roles/thin-client/identity/local-users.nix
+#
+# Local break-glass users for Thin Clients. These exist independently of
+# AD/DNS/NetBird availability. Used for disaster recovery via NetBird SSH.
+#
+# NOTE: This intentionally does NOT import the m3ta-home profile system
+# from hosts/common/users/. Thin Clients are not dev machines and don't
+# need home-manager profiles — just a lean account with password, SSH key,
+# and wheel membership.
+{
+  config,
+  lib,
+  ...
+}: let
+  inherit (lib) mkIf;
+  cfg = config.az.tc;
+in {
+  config = mkIf cfg.enable {
+    users.users."sascha.koenig" = {
+      # Re-uses the existing hashedPassword from hosts/common/users/sascha.koenig.nix
+      hashedPassword = "$y$j9T$ORX4btVZgs9Xjq2oIvzJm0$lXiPwaa0D6t.eMDIx1UBesEAMOkWXBoGwpeI7X0aS8D";
+      isNormalUser = true;
+      shell = config.users.defaultUserShell;
+      extraGroups = ["wheel" "networkmanager" "plugdev" "input"];
+      openssh.authorizedKeys.keys = [
+        "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIEZbg/Z9mnflXuLahGY8WOSBMqbgeqVIkIwRkquys1Ml sascha.koenig@azintec.com"
+      ];
+    };
+
+    users.users."jannik.mueller" = {
+      # Re-uses the existing hashedPassword from hosts/common/users/jannik.mueller.nix
+      hashedPassword = "$y$j9T$09RgD3AU3PK9Oi6JGLe0V1$i8J2ZOD1h1b6Zpw28ub.kExujoDKHzokeXzkM23Tfd/";
+      isNormalUser = true;
+      shell = config.users.defaultUserShell;
+      extraGroups = ["wheel" "networkmanager" "plugdev" "input"];
+      openssh.authorizedKeys.keys = [
+        "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIPvZazSuIoWoRWhkAqQDMLeurxVUyy1MTllp1wfw1tzq"
+      ];
+    };
+  };
+}