Repos: Empty Sources, Deb822 & Security Fixes

- Enhanced repository detection logic in `modules/repos/repo_detect.sh`. Implemented `has_active_deb_sources()` for content-aware scanning across `sources.list`, `*.list`, and `*.sources` files. Empty or comment-only files are now correctly identified as "none" to trigger bootstrapping.
- Enforced Debian 13 (Trixie) specific logic in `detect_repo_format()`. Deb822 format is only applied when `debian.sources` is active; Bookworm and Bullseye systems default strictly to classic sources.list regardless of file presence.
- Added state guard against mixed configuration formats (deb822 + classic active simultaneously) with a warning prompt before writing, preventing duplicate entries in `/etc/apt/sources.list`.
- Rewrote `_repos_enable_components()` in `modules/repos.sh` to remove early returns when components are already enabled. The script now verifies and ensures security and updates sections exist/were written correctly if missing or different.
- Created new `bootstrap_repositories()` function for systems with no active sources. Includes user dialogue for format selection (Trixie) or auto-classic (older versions), backup/restore safety, and cleanup of empty sources.list files post-bootstrap.
- Fixed false success reporting in `modules/firmware.sh` and `gaming.sh`. Added pre-checks to ensure APT sources exist before attempting `sed -i` modifications; if sources are missing, the script now triggers a full repository bootstrap instead of silently failing.
- Implemented post-write verification in firmware/gaming modules to confirm components were actually added before reporting success to the user.
- Generalized backports detection in `modules/utils.sh` (`is_backports_enabled()`) to scan all `*.list` and `*.sources` files rather than relying on fixed canonical filenames.
- Corrected test harness variable expansion order and trimmed whitespace from component parsing logic during development verification.

modules/utils.sh

@@ -505,14 +505,13 @@ is_backports_enabled() {
         echo true; return
     fi
 
-    # Classic standalone (new — debian-backports.list)
-    if [ -f /etc/apt/sources.list.d/debian-backports.list ] && \
-       grep -Eq "$c_pattern" /etc/apt/sources.list.d/debian-backports.list 2>/dev/null; then
+    # Classic standalone (any .list file in sources.list.d)
+    if [ -d /etc/apt/sources.list.d ] && grep -qrE "$c_pattern" /etc/apt/sources.list.d/*.list 2>/dev/null; then
         echo true; return
     fi
 
     # Deb822 any .sources file
-    if grep -qr "$d_pattern" /etc/apt/sources.list.d/*.sources 2>/dev/null; then
+    if [ -d /etc/apt/sources.list.d ] && grep -qr "$d_pattern" /etc/apt/sources.list.d/*.sources 2>/dev/null; then
         echo true; return
     fi