refactor: improve script modularity and logging consistency

- Updated `scripts/generate-changelog.sh` to use `log_info` and `log_error` for all outputs.
- Moved `source` statements for utility files to the top of the script.
- Refactored `scripts/install-git-cliff.sh` to replace `echo` with logging functions.
- Ensured consistent error handling and logging across all scripts.

scripts/generate-changelog.sh

@@ -18,6 +18,9 @@
 #   • Generates the changelog; removes a leading empty line.
 set -euo pipefail
 
+source "$(dirname "$0")/../lib/utils.sh"
+source "$(dirname "$0")/../lib/logging.sh"
+
 # ───────────────────────────────────────────────
 CONFIG_FILE=""
 TAG=""
@@ -40,8 +43,8 @@ while [[ $# -gt 0 ]]; do
 done
 
 # 2 Basic validation
-[[ -z "$CONFIG_FILE" || -z "$TAG" ]] && { echo "❌ --config and --tag are required"; show_help; exit 1; }
-[[ "$DEBUG" = false && -z "$OUT_FILE" ]] && { echo "❌ --out is required unless --debug is set"; show_help; exit 1; }
+[[ -z "$CONFIG_FILE" || -z "$TAG" ]] && { log_error "--config and --tag are required"; show_help; exit 1; }
+[[ "$DEBUG" = false && -z "$OUT_FILE" ]] && { log_error "--out is required unless --debug is set"; show_help; exit 1; }
 [[ ! -r "$CONFIG_FILE" ]] && { log_error "Config file not found or unreadable: $CONFIG_FILE"; exit 1; }
 if [[ "$DEBUG" = false ]]; then
   OUT_DIR=$(dirname "$OUT_FILE")