Remove remaining OS-specific hardcodes from core scripts

OS version reads now go through platform_get_os_version() and
platform_os_version_probe_cmd() instead of grepping /etc/unraid-version directly.

STATE_DIR fallbacks to /boot/config removed — STATE_DIR is always set by
load_config.sh and the fallback encoded a platform-specific path.

Setup DB path references use platform_setup_db_path() instead of the
VARAVERK_SETUP_FILE/-/boot/config compound fallback.

DOCKER_APPDATA_BASE default removed from arr_sync.sh — the adapter sets it.

common.sh

@@ -81,7 +81,7 @@
 #
 #            Three new safety functions added:
 #            check_unraid_version_parity() — refuses remote ops on version mismatch
-#              reads /etc/unraid-version local and remote via SSH
+#              reads OS version via platform_get_os_version() / platform_os_version_probe_cmd()
 #              major mismatch → abort | minor mismatch → configurable warn/abort
 #            check_remote_docker_daemon() — verifies remote Docker daemon before
 #              issuing any remote container commands — strike system → skip/retry/exit
@@ -1741,7 +1741,7 @@ check_api() {
 # remote operation. Version mismatches can mean changed APIs, commands, or behaviours
 # that silently break remote container operations, rsync, or fallback logic.
 #
-# Reads /etc/unraid-version on both sides — format: version="7.2.3"
+# Reads platform OS version on both sides via adapter.
 #
 # Mismatch behaviour (UNRAID_VERSION_MISMATCH_ACTION in master.conf):
 #   "warn"  — log warning and continue (default for minor/patch differences)
@@ -1754,28 +1754,26 @@ check_unraid_version_parity() {
     local local_version remote_version
 
     # Read local version
-    if [[ ! -f /etc/unraid-version ]]; then
-        warn "Cannot read local /etc/unraid-version — skipping version parity check"
-        return 0
-    fi
-    local_version=$(grep -oP '(?<=version=")[^"]+' /etc/unraid-version 2>/dev/null)
+    local_version=$(platform_get_os_version 2>/dev/null)
     if [[ -z "$local_version" ]]; then
-        warn "Cannot parse local unRAID version — skipping parity check"
+        warn "Cannot read local OS version — skipping version parity check"
         return 0
     fi
 
     # Read remote version via SSH
+    local _probe_cmd
+    _probe_cmd=$(platform_os_version_probe_cmd)
     remote_version=$(ssh -i "$SSH_KEY" -o ConnectTimeout=10 root@"$REMOTE_SERVER" \
-        "grep -oP '(?<=version=\")[^\"]+' /etc/unraid-version 2>/dev/null" 2>/dev/null)
+        "$_probe_cmd" 2>/dev/null)
     if [[ -z "$remote_version" ]]; then
-        warn "Cannot read remote unRAID version from $REMOTE_SERVER_NAME — skipping parity check"
+        warn "Cannot read remote OS version from $REMOTE_SERVER_NAME — skipping parity check"
         return 0
     fi
 
     log "Version parity: local=$local_version remote=$remote_version"
 
     if [[ "$local_version" == "$remote_version" ]]; then
-        log "unRAID versions match: $local_version ✅"
+        log "OS versions match: $local_version ✅"
         return 0
     fi
 
@@ -1785,20 +1783,22 @@ check_unraid_version_parity() {
     remote_major="${remote_version%%.*}"
 
     if [[ "$local_major" != "$remote_major" ]]; then
-        error "unRAID MAJOR version mismatch — local: $local_version remote: $remote_version"
+        error "OS MAJOR version mismatch — local: $local_version remote: $remote_version"
         error "Major version differences may break remote APIs, commands, and behaviours"
         error "Update both servers to the same major version before running remote operations"
-        notify "unRAID major version mismatch on $(hostname) — local: $local_version remote: $remote_version — remote operations aborted"             "Version Parity" "warning"
+        notify "OS major version mismatch on $(hostname) — local: $local_version remote: $remote_version — remote operations aborted" \
+            "Version Parity" "warning"
         return 1
     fi
 
     # Minor/patch mismatch — action depends on config
     local action="${UNRAID_VERSION_MISMATCH_ACTION:-warn}"
-    warn "unRAID version mismatch — local: $local_version remote: $remote_version"
+    warn "OS version mismatch — local: $local_version remote: $remote_version"
 
     if [[ "$action" == "abort" ]]; then
         error "UNRAID_VERSION_MISMATCH_ACTION=abort — refusing to continue"
-        notify "unRAID version mismatch on $(hostname) — local: $local_version remote: $remote_version — aborted"             "Version Parity" "warning"
+        notify "OS version mismatch on $(hostname) — local: $local_version remote: $remote_version — aborted" \
+            "Version Parity" "warning"
         return 1
     fi
 
@@ -1906,14 +1906,14 @@ validate_unraid_cmd() {
 
 show_status() {
     local local_ver
-    local_ver=$(grep -oP '(?<=version=")[^"]+' /etc/unraid-version 2>/dev/null || echo "unknown")
+    local_ver=$(platform_get_os_version 2>/dev/null || echo "unknown")
     echo "━━━━━ $ICON_SUMMARY STATUS ━━━━━"
     echo "Local:        $LOCAL_SERVER_NAME"
     echo "Remote:       $REMOTE_SERVER_NAME"
     echo "IP:           ${REMOTE_SERVER:-not resolved}"
     echo "My ID:        ${MY_ID:-not set}"
     echo "Remote ID:    ${REMOTE_ID:-not set}"
-    echo "unRAID ver:   $local_ver"
+    echo "OS ver:       $local_ver"
     echo "Profile:      ${PROFILE_NAME:-n/a}"
 
     echo "DryRun:       ${DRY_RUN:-false}"