Migrate Authelia addon; fix real config-clobbering bug in save_config; bump to v2.6.0

Second Addon migrated: menus/addon_authelia.sh (encrypted SSO
credentials, AES-256-CBC with a key derived from /etc/machine-id via
scrypt - same algorithm main.js decrypts with - plus the full
Dockerized server-side setup instructions, now viewable again later
without reconfiguring).

Investigating how to wire its three config.json fields (autheliaURL/
autheliaUsername/autheliaEncryptedPassword) into lib/config.sh surfaced
a real, currently-shipping bug that has nothing to do with Authelia
specifically: save_config() did a full `jq -n` rebuild of config.json
from a fixed list of known fields - identical to what the legacy
script's own save_config still does. The legacy configure_authelia()
writes its three fields via a careful `. + {...}` merge that preserves
everything else already in the file, but neither save_config knew those
fields existed - so the next time a user visited Sites, Touch Controls,
Navigation, or Password Protection (all of which call save_config),
their Authelia credentials were silently deleted. This bug already
existed in the shipped single-file installer; it was ported faithfully
into lib/config.sh's first version because no test happened to set an
untracked field before calling save_config.

Fixed in lib/config.sh: save_config now merges its known fields onto
whatever's already in config.json (jq `. + {...}`) instead of rebuilding
the file from nothing, with a `jq empty` validity check falling back to
`{}` if the existing file is missing or corrupt. Any field this tool
doesn't track - Authelia's three today, anything else a future addon
adds tomorrow - now survives automatically. autheliaURL/
autheliaUsername/autheliaEncryptedPassword are also tracked fields in
their own right now (load_existing_config/save_config), consistent with
every other config.json field this tool manages, giving Authelia both a
direct fix and the general safety net.

The equivalent bug still exists, unfixed, in ubuntu-based-kiosk.sh's own
save_config - noted in both that script's changelog and the Readme's
"Modular Management" section as an open question: whether to backport
just that one fix into the legacy script now, independent of the wider
migration, given it's a real credential-loss bug affecting the
currently-shipping installer today.

Verified:
- New dedicated test (test_save_merge.sh) proving the save_config fix
  itself: seeded config.json with a simulated untracked field via the
  same `. + {...}` merge Authelia's own code uses, called save_config
  from an unrelated context (Sites deleting a tab), and confirmed the
  untracked field survived while the tab deletion still correctly took
  effect (not undone by the merge) - plus corrupt-JSON and
  missing-file edge cases both handled without crashing.
- New scratch-config test for addon_authelia.sh using REAL encryption
  (this sandbox has both Node and /etc/machine-id): configured with a
  real password, then decrypted the stored ciphertext using main.js's
  exact algorithm (independently reproduced in the test) and confirmed
  it recovers the original password exactly - true interoperability,
  not just "some ciphertext was produced." Also covered cancel paths,
  clearing the configuration, the encryption-unavailable failure path,
  and confirmed Authelia's config survives an unrelated Sites save.
- Full regression: re-ran all 9 prior scratch/stub test suites after
  both the lib/config.sh changes - all still clean.
- End-to-end: ran the real install.sh as a genuine non-root, non-
  "kiosk" user with a seeded minimal config.json, through Addons ->
  Authelia -> Configure with a real URL/username/password -> confirmed
  the resulting config.json on disk, and independently decrypted the
  stored password for real using main.js's algorithm to confirm it
  matches exactly. Clean exit code 0 throughout.

lib/config.sh

@@ -60,6 +60,9 @@ LOCKOUT_AT_TIME=""
 LOCKOUT_ACTIVE_START=""
 LOCKOUT_ACTIVE_END=""
 REQUIRE_PASSWORD_ON_BOOT="false"
+AUTHELIA_URL=""
+AUTHELIA_USERNAME=""
+AUTHELIA_ENCRYPTED_PASSWORD=""
 
 kiosk_user_exists() {
     id "$KIOSK_USER" &>/dev/null
@@ -125,6 +128,10 @@ load_existing_config() {
 
     boot_password=$(sudo -u "$KIOSK_USER" jq -r '.requirePasswordOnBoot // false' "$CONFIG_PATH" 2>/dev/null)
     [[ "$boot_password" == "true" ]] && REQUIRE_PASSWORD_ON_BOOT="true" || REQUIRE_PASSWORD_ON_BOOT="false"
+
+    AUTHELIA_URL=$(sudo -u "$KIOSK_USER" jq -r '.autheliaURL // ""' "$CONFIG_PATH" 2>/dev/null || echo "")
+    AUTHELIA_USERNAME=$(sudo -u "$KIOSK_USER" jq -r '.autheliaUsername // ""' "$CONFIG_PATH" 2>/dev/null || echo "")
+    AUTHELIA_ENCRYPTED_PASSWORD=$(sudo -u "$KIOSK_USER" jq -r '.autheliaEncryptedPassword // ""' "$CONFIG_PATH" 2>/dev/null || echo "")
 }
 
 # Write every bash global back out to config.json, then offer to reload the
@@ -159,7 +166,28 @@ save_config() {
     local boot_password_json="false"
     [[ "$REQUIRE_PASSWORD_ON_BOOT" == "true" ]] && boot_password_json="true"
 
-    jq -n \
+    # Merge onto whatever's already in config.json rather than rebuilding
+    # the file from nothing. The legacy save_config did a full `jq -n`
+    # rebuild listing every known field - any field it doesn't know about
+    # (e.g. Authelia's autheliaURL/autheliaUsername/
+    # autheliaEncryptedPassword, written by its own careful `. + {...}`
+    # merge) gets silently DELETED the next time any other menu that
+    # calls save_config runs. Real, currently-shipping bug in the legacy
+    # script, not unique to this migration - ported faithfully into this
+    # file's first version because no test happened to set an untracked
+    # field first. `. + {known fields...}` below preserves anything this
+    # tool doesn't track while still fully replacing every field it does
+    # (including tabs, via the same array-rebuild loop as before) - jq's
+    # `+` on objects takes the right-hand value for any key present on
+    # both sides, so a fully-specified `tabs` here still discards a
+    # deleted tab rather than merging old and new.
+    local existing="{}"
+    if sudo -u "$KIOSK_USER" test -f "$CONFIG_PATH" 2>/dev/null; then
+        existing=$(sudo -u "$KIOSK_USER" cat "$CONFIG_PATH" 2>/dev/null)
+        echo "$existing" | jq empty 2>/dev/null || existing="{}"
+    fi
+
+    echo "$existing" | jq \
         --argjson autoswitch true \
         --argjson enableTouch true \
         --argjson dualSwipe "$dual_json" \
@@ -177,7 +205,10 @@ save_config() {
         --arg lockoutActiveStart "${LOCKOUT_ACTIVE_START:-}" \
         --arg lockoutActiveEnd "${LOCKOUT_ACTIVE_END:-}" \
         --argjson requirePasswordOnBoot "$boot_password_json" \
-        '{autoswitch:$autoswitch,enableTouch:$enableTouch,dualSwipe:$dualSwipe,swipeMode:$swipeMode,allowNavigation:$allowNavigation,homeTabIndex:$homeTabIndex,inactivityTimeout:$inactivityTimeout,enablePauseButton:$enablePauseButton,enableKeyboardButton:$enableKeyboardButton,enableNavButton:$enableNavButton,enablePasswordProtection:$enablePasswordProtection,lockoutPassword:$lockoutPassword,lockoutTimeout:$lockoutTimeout,lockoutAtTime:$lockoutAtTime,lockoutActiveStart:$lockoutActiveStart,lockoutActiveEnd:$lockoutActiveEnd,requirePasswordOnBoot:$requirePasswordOnBoot,tabs:[]}' > "$tmp"
+        --arg autheliaURL "${AUTHELIA_URL:-}" \
+        --arg autheliaUsername "${AUTHELIA_USERNAME:-}" \
+        --arg autheliaEncryptedPassword "${AUTHELIA_ENCRYPTED_PASSWORD:-}" \
+        '. + {autoswitch:$autoswitch,enableTouch:$enableTouch,dualSwipe:$dualSwipe,swipeMode:$swipeMode,allowNavigation:$allowNavigation,homeTabIndex:$homeTabIndex,inactivityTimeout:$inactivityTimeout,enablePauseButton:$enablePauseButton,enableKeyboardButton:$enableKeyboardButton,enableNavButton:$enableNavButton,enablePasswordProtection:$enablePasswordProtection,lockoutPassword:$lockoutPassword,lockoutTimeout:$lockoutTimeout,lockoutAtTime:$lockoutAtTime,lockoutActiveStart:$lockoutActiveStart,lockoutActiveEnd:$lockoutActiveEnd,requirePasswordOnBoot:$requirePasswordOnBoot,autheliaURL:$autheliaURL,autheliaUsername:$autheliaUsername,autheliaEncryptedPassword:$autheliaEncryptedPassword,tabs:[]}' > "$tmp"
 
     if [[ ${#URLS[@]} -gt 0 ]]; then
         for idx in "${!URLS[@]}"; do