feat(web): weekly automatic updates with health check and rollback

A General-tab toggle (off by default) checks for and installs LEDMatrix and
plugin updates once a week, overnight in the configured timezone.

- Pre-update checks skip (and report) instead of forcing: local edits or
  commits, merge/live rebase, no upstream, low disk, missing health check, or
  a version that was already rolled back. An abandoned rebase (HEAD back on a
  branch) is cleared, since it would otherwise block every pull.
- The pull reuses the Update Code path (now perform_core_update(), which
  reports dependency install failures as data).
- ledmatrix-update-verify.service, started via a .path unit from a request
  file, restarts the services from its own cgroup, requires them to come up
  and stay up, and otherwise resets to the previous commit and reinstalls the
  previous requirements. It runs a copy of the checker taken before the pull.
- No SSH needed: switching the toggle on restarts the display service, which
  (as root) installs the two units from the repo templates for the web user.
  first_time_install.sh installs them too and takes --enable-auto-update /
  LEDMATRIX_AUTO_UPDATE (passed through by one-shot-install.sh).
- Plugins update after the code passes its check; failures, blocks and
  rollbacks raise an Overview banner and show under the toggle.

Tested end to end on a Pi: web-UI setup, a good update, a broken web service
and a broken display (both rolled back), a blocked local edit, and an
abandoned rebase found on the device.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

first_time_install.sh

@@ -154,6 +154,8 @@ SKIP_PERF=${LEDMATRIX_SKIP_PERF:-0}
 SKIP_REBOOT_PROMPT=${LEDMATRIX_SKIP_REBOOT_PROMPT:-0}
 SKIP_SWAP=${LEDMATRIX_SKIP_SWAP:-0}
 BUILD_JOBS_OVERRIDE=${LEDMATRIX_BUILD_JOBS:-}
+# Weekly automatic updates: 1 on, 0 off, empty = ask (interactive) or leave as is.
+AUTO_UPDATE=${LEDMATRIX_AUTO_UPDATE:-}
 
 usage() {
     cat <<USAGE
@@ -168,12 +170,15 @@ Options:
       --skip-swap           Never add temporary swap for the C++ build
       --build-jobs N        Compile the C++ library with N parallel jobs
                             (default: scaled to available RAM)
+      --enable-auto-update  Turn on weekly automatic updates (with health
+                            check and automatic rollback)
+      --no-auto-update      Leave weekly automatic updates off
   -h, --help                Show this help message and exit
 
 Environment variables (same effect as flags):
   LEDMATRIX_ASSUME_YES=1, RPI_RGB_FORCE_REBUILD=1, LEDMATRIX_SKIP_SOUND=1,
   LEDMATRIX_SKIP_PERF=1, LEDMATRIX_SKIP_REBOOT_PROMPT=1,
-  LEDMATRIX_SKIP_SWAP=1, LEDMATRIX_BUILD_JOBS=N
+  LEDMATRIX_SKIP_SWAP=1, LEDMATRIX_BUILD_JOBS=N, LEDMATRIX_AUTO_UPDATE=1|0
 
 Low-memory devices:
   On a Pi with under 2GB of RAM the C++ build is limited to fewer parallel
@@ -191,6 +196,8 @@ while [ $# -gt 0 ]; do
         --skip-perf) SKIP_PERF=1 ;;
         --no-reboot-prompt) SKIP_REBOOT_PROMPT=1 ;;
         --skip-swap) SKIP_SWAP=1 ;;
+        --enable-auto-update) AUTO_UPDATE=1 ;;
+        --no-auto-update) AUTO_UPDATE=0 ;;
         --build-jobs)
             shift
             if [ $# -eq 0 ]; then echo "--build-jobs requires a number"; usage; exit 1; fi
@@ -797,6 +804,35 @@ else
     echo "✓ Main config file already exists"
 fi
 
+# Weekly automatic updates (General tab -> Automatic Updates). Off unless asked
+# for: --enable-auto-update / LEDMATRIX_AUTO_UPDATE=1, or "y" at the prompt when
+# installing interactively. Only an explicit choice changes the setting, so
+# re-running the installer with -y never switches it silently.
+if [ -z "$AUTO_UPDATE" ] && [ "$ASSUME_YES" != "1" ] && [ -t 0 ]; then
+    read -p "Automatically check for and install LEDMatrix updates once a week, with automatic rollback if an update breaks something? (y/N): " -n 1 -r
+    echo
+    if [[ $REPLY =~ ^[Yy]$ ]]; then AUTO_UPDATE=1; else AUTO_UPDATE=0; fi
+fi
+if [ "$AUTO_UPDATE" = "1" ] || [ "$AUTO_UPDATE" = "0" ]; then
+    if python3 - "$PROJECT_ROOT_DIR/config/config.json" "$AUTO_UPDATE" <<'PY'
+import json, sys
+path, enabled = sys.argv[1], sys.argv[2] == "1"
+with open(path, encoding="utf-8") as f:
+    config = json.load(f)
+if not isinstance(config.get("auto_update"), dict):
+    config["auto_update"] = {}
+config["auto_update"]["enabled"] = enabled
+with open(path, "w", encoding="utf-8") as f:
+    json.dump(config, f, indent=4)
+    f.write("\n")
+PY
+    then
+        if [ "$AUTO_UPDATE" = "1" ]; then echo "✓ Weekly automatic updates enabled"; else echo "✓ Weekly automatic updates off"; fi
+    else
+        echo "⚠ Could not set auto_update in config/config.json; turn it on from the General tab instead"
+    fi
+fi
+
 # Create config_secrets.json from template if missing
 if [ ! -f "$PROJECT_ROOT_DIR/config/config_secrets.json" ]; then
     if [ -f "$PROJECT_ROOT_DIR/config/config_secrets.template.json" ]; then
@@ -1272,7 +1308,7 @@ if [ -f "$PROJECT_ROOT_DIR/scripts/install/install_web_service.sh" ]; then
         fi
     fi
     
-    if [ ! -f "/etc/systemd/system/ledmatrix-web.service" ] || [ "$NEEDS_UPDATE" = true ]; then
+    if [ ! -f "/etc/systemd/system/ledmatrix-web.service" ] || [ ! -f "/etc/systemd/system/ledmatrix-update-verify.path" ] || [ "$NEEDS_UPDATE" = true ]; then
         bash "$PROJECT_ROOT_DIR/scripts/install/install_web_service.sh"
         # Ensure systemd sees any new/changed unit files
         systemctl daemon-reload || true
@@ -1288,7 +1324,7 @@ echo ""
 CURRENT_STEP="Harden systemd unit file permissions"
 echo "Step 8.1: Setting systemd unit file permissions..."
 echo "-----------------------------------------------"
-for unit in "/etc/systemd/system/ledmatrix.service" "/etc/systemd/system/ledmatrix-web.service" "/etc/systemd/system/ledmatrix-wifi-monitor.service"; do
+for unit in "/etc/systemd/system/ledmatrix.service" "/etc/systemd/system/ledmatrix-web.service" "/etc/systemd/system/ledmatrix-wifi-monitor.service" "/etc/systemd/system/ledmatrix-update-verify.service" "/etc/systemd/system/ledmatrix-update-verify.path"; do
     if [ -f "$unit" ]; then
         chown root:root "$unit" || true
         chmod 644 "$unit" || true