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

- caddy: security headers (X-Content-Type-Options/X-XSS-Protection/
  X-Frame-Options) on all vhosts + baseline CSP; strip SnappyMail
  upstream copies via header_down on mail.severijnse.eu
- tlsa-updater: compute TLSA 3 1 1 from cert SPKI (SHA-256), sync
  _25/_465/_993, fail-safe placeholders; coredns zone updated
- pre-commit: wire cachix/git-hooks.nix (alejandra, statix, actionlint,
  ...); CI pre-commit job over x86_64 + aarch64 matrix
- gitea: enable Gitea Actions + self-hosted runner (native:host,
  aarch64 via binfmt); add .gitea/workflows/ci.yml and local hook
- fix statix warnings (merge repeated systemd/database/configFile keys,
  inherit, bool-compare guards); add missing trailing newlines

home/terminal/software/xdg.nix

@@ -80,19 +80,21 @@ in {
       enable = true;
       defaultApplications = associations;
     };
-    configFile."xdg-desktop-portal-termfilechooser/config".text = ''
-      [filechooser]
-      cmd=${yaziWrapper}/bin/yazi-wrapper
-      default_dir=$HOME
-      open_mode=suggested
-      save_mode=suggested
-    '';
-    configFile."user-dirs.dirs".source = userDirsConfig;
-    configFile."mimeapps.list".text = ''
-      [Default Applications]
-      ${lib.concatStringsSep "\n" (lib.mapAttrsToList (k: v: "${k}=${lib.concatStringsSep ";" v}") associations)}
-      [Added Associations]
-      ${lib.concatStringsSep "\n" (lib.mapAttrsToList (k: v: "${k}=${lib.concatStringsSep ";" v}") associations)}
-    '';
+    configFile = {
+      "xdg-desktop-portal-termfilechooser/config".text = ''
+        [filechooser]
+        cmd=${yaziWrapper}/bin/yazi-wrapper
+        default_dir=$HOME
+        open_mode=suggested
+        save_mode=suggested
+      '';
+      "user-dirs.dirs".source = userDirsConfig;
+      "mimeapps.list".text = ''
+        [Default Applications]
+        ${lib.concatStringsSep "\n" (lib.mapAttrsToList (k: v: "${k}=${lib.concatStringsSep ";" v}") associations)}
+        [Added Associations]
+        ${lib.concatStringsSep "\n" (lib.mapAttrsToList (k: v: "${k}=${lib.concatStringsSep ";" v}") associations)}
+      '';
+    };
   };
 }