Harden server and add Nix-native CI + self-hosted Gitea Actions

- Add self-hosted Gitea Actions runner module (servers/hetzner/modules/services/gitea.nix)
- Add CI workflow (.gitea/workflows/ci.yml):
  - Flake check (x86_64-linux + aarch64-linux, eval-only)
  - Pre-commit checks (x86_64-linux only)
  - Gitea-native runner (no Docker); Nix from host PATH
  - NIX_CONFIG enables flakes + extra-platforms
- Remove redundant .github/workflows/ci.yml (shadows .gitea)
- Enable deadnix in pre-commit hooks (flake.nix), fix 38 files
- Add statix.toml disabling empty_pattern lint (nixpkgs standard)
- Format whole repo with alejandra (27 files)
- Fix CI nix-not-found: export /run/current-system/sw/bin in PATH
- Remove aarch64 from pre-commit matrix (no QEMU binfmt deployed yet)

servers/hetzner/hosts/hetzner/default.nix

@@ -1,9 +1,4 @@
-{
-  config,
-  pkgs,
-  lib,
-  ...
-}: {
+{...}: {
   imports = [
     ./networking.nix
     ./users.nix

servers/hetzner/hosts/hetzner/hardware-configuration.nix

@@ -2,9 +2,7 @@
 # and may be overwritten by future invocations.  Please make changes
 # to /etc/nixos/configuration.nix instead.
 {
-  config,
   lib,
-  pkgs,
   modulesPath,
   ...
 }: {

servers/hetzner/hosts/hetzner/hardware.nix

@@ -1,9 +1,4 @@
-{
-  config,
-  pkgs,
-  lib,
-  ...
-}: {
+{...}: {
   boot = {
     loader = {
       grub = {

servers/hetzner/hosts/hetzner/networking.nix

@@ -1,9 +1,4 @@
-{
-  config,
-  pkgs,
-  lib,
-  ...
-}: {
+{...}: {
   networking = {
     hostName = "debian-4gb-fsn1-1";
     domain = "severijnse.eu";

servers/hetzner/hosts/hetzner/users.nix

@@ -1,9 +1,4 @@
-{
-  config,
-  pkgs,
-  lib,
-  ...
-}: {
+{pkgs, ...}: {
   users.users = {
     root = {
       openssh.authorizedKeys.keys = [