Refactored installer into modular library structure with improved error handling and logging.

The changes include:
- Split monolithic script into lib/, config/, profiles/, and files/ directories
- Added error handling with cleanup on failure
- Added installation logging to /var/log/arch-install.log
- Added username validation

lib/system/locale.sh

@@ -0,0 +1,43 @@
+#!/bin/bash
+
+# Copyright 2026 Logan Fick
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# locale.sh - Locale and timezone configuration
+#
+# Configures locale (en_US.UTF-8) and runs systemd-firstboot for timezone,
+# keymap, and hostname setup.
+
+# Configure system locale (en_US.UTF-8)
+configure_locale() {
+    print "Setting up locale..."
+
+    chroot_run sed -i '/^#.*en_US.UTF-8 UTF-8/s/^#//' /etc/locale.gen
+    run_visible_cmd chroot_run locale-gen
+    chroot_run systemd-firstboot --locale=en_US.UTF-8
+}
+
+# Run interactive firstboot setup for timezone, keymap, hostname
+run_firstboot() {
+    print "Entering first time setup..."
+    print "Your keymap is probably 'us' and the time zone is probably 'America/New_York'."
+
+    run_visible_cmd chroot_run systemd-firstboot --prompt
+}
+
+# Full locale and timezone setup
+setup_locale() {
+    configure_locale
+    run_firstboot
+}