PHP app layer: consolidate common functions, fix critical bugs, standardize patterns

Consolidations (config.php gains 5 shared utilities):
- vv_format_uptime() replaces 4 inline uptime-formatting blocks
- vv_parse_conf_scalar() replaces vv_arr_scalar/vv_wd_scalar/vv_fb_scalar/vv_media_conf_scalar
- vv_known_hosts() replaces vv_arr_known_hosts/vv_fb_known_hosts + inline parser in watchdog
- vv_parse_kv_db() replaces inline key=value parsing in snapshot and monitor
- vv_local_ip() replaces duplicate in docker_folders.php and inline in docker.php
All module-level function names kept as thin aliases so call sites unchanged.

Critical bug fixes:
- api/system.php: added require_once config.php and POST-only guard (no auth on shutdown)
- api/movescript.php + reorderarray.php: use vv_write_conf_raw (atomic) + vv_push_master_conf
- api/snapshot.php: share /tmp/vv_cpu_stat.json with vv_cpu_per_core() instead of own state file

Correctness:
- vv_cpu_per_core() and vv_network_stats(): atomic tmp+rename for state files (concurrent poll safety)
- ext_ip curl cache moved from /tmp/vv_ext_ip.cache to vv_cache_read/write (canonical cache dir)
- monitor_remote.php + board.php + snapshot.php: all use vv_cache_read/write instead of ad-hoc /tmp files

HTTP method guards added to write-only APIs that were missing them:
- api/scheduler.php, conf_toggle.php, flag_toggle.php

Plugin/unraid/include/arrs.php

@@ -6,23 +6,11 @@ require_once __DIR__ . '/config.php';
 // ── Conf helpers ──────────────────────────────────────────────────────────────
 
 function vv_arr_scalar(string $raw, string $key): string {
-    return preg_match('/^\s*' . preg_quote($key, '/') . '\s*=\s*"?([^"\n]*)"?/m', $raw, $m)
-        ? trim($m[1]) : '';
+    return vv_parse_conf_scalar($raw, $key);
 }
 
-// Returns all configured hosts found in master.conf as ['host1'=>'hostname', ...]
-// Returns ['host1' => 'hostname', 'host2' => 'hostname', ...] from master.conf.
-// Matches both HOST1="name" and HOST1_NAME="name" (either convention).
 function vv_arr_known_hosts(): array {
-    $vars  = vv_conf_vars();   // already parses HOST1="val" correctly
-    $hosts = [];
-    foreach ($vars as $k => $v) {
-        if (preg_match('/^HOST(\d+)$/', $k, $m) && $v !== '') {
-            $hosts['host' . $m[1]] = $v;
-        }
-    }
-    ksort($hosts);
-    return $hosts ?: ['host1' => 'HOST1'];
+    return vv_known_hosts();
 }
 
 function vv_arr_node_names(): array {