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/common.php

@@ -23,13 +23,10 @@ function vv_system_info(): array {
         $uptimeRaw = $os['uptime'] ?? '';
         if (is_numeric($uptimeRaw)) {
             $uptimeSec = (int)$uptimeRaw;
-            $days  = intdiv($uptimeSec, 86400);
-            $hours = intdiv($uptimeSec % 86400, 3600);
-            $mins  = intdiv($uptimeSec % 3600, 60);
-            $uptime = ($days ? "{$days}d " : '') . ($hours ? "{$hours}h " : '') . "{$mins}m";
+            $uptime    = vv_format_uptime($uptimeSec);
         } else {
             $uptimeSec = 0;
-            $uptime = $uptimeRaw ?: '—';
+            $uptime    = $uptimeRaw ?: '—';
         }
 
         $load = sys_getloadavg();
@@ -57,10 +54,7 @@ function vv_system_info(): array {
         if (preg_match('/^model name\s*:\s*(.+)/', $line, $m)) { $cpuModel = trim($m[1]); break; }
     }
     $uptimeSec = (int)explode(' ', @file_get_contents('/proc/uptime') ?: '0')[0];
-    $days  = intdiv($uptimeSec, 86400);
-    $hours = intdiv($uptimeSec % 86400, 3600);
-    $mins  = intdiv($uptimeSec % 3600, 60);
-    $uptime = ($days ? "{$days}d " : '') . ($hours ? "{$hours}h " : '') . "{$mins}m";
+    $uptime    = vv_format_uptime($uptimeSec);
 
     $load = sys_getloadavg();
     return [
@@ -159,7 +153,10 @@ function vv_cpu_per_core(): array {
 
     $stateFile = '/tmp/vv_cpu_stat.json';
     $prev = file_exists($stateFile) ? (json_decode(file_get_contents($stateFile), true) ?: []) : [];
-    file_put_contents($stateFile, json_encode($raw));
+    // Atomic write — concurrent fast/slow polls read a consistent snapshot
+    $tmp = $stateFile . '.tmp';
+    file_put_contents($tmp, json_encode($raw));
+    rename($tmp, $stateFile);
 
     $usage = function(array $c, ?array $p): int {
         if (!$p) return 0;
@@ -298,7 +295,9 @@ function vv_network_stats(): array {
     $stateFile = '/tmp/vv_net_stat.json';
     $now  = ['rx' => $rxBytes, 'tx' => $txBytes, 'ts' => microtime(true)];
     $prev = file_exists($stateFile) ? (json_decode(file_get_contents($stateFile), true) ?: []) : [];
-    file_put_contents($stateFile, json_encode($now));
+    $tmp = $stateFile . '.tmp';
+    file_put_contents($tmp, json_encode($now));
+    rename($tmp, $stateFile);
 
     $rxRate = $txRate = 0;
     if (!empty($prev['ts']) && ($dt = $now['ts'] - $prev['ts']) > 0.1) {
@@ -314,15 +313,15 @@ function vv_network_stats(): array {
     ) ?: '');
 
     // External IP — curl ifconfig.me, cached 5 min so we don't hammer it
-    $extIpCache = '/tmp/vv_ext_ip.cache';
-    $extIp = '';
-    if (file_exists($extIpCache) && (time() - filemtime($extIpCache)) < 300) {
-        $extIp = trim(file_get_contents($extIpCache) ?: '');
+    $extIp   = '';
+    $extData = vv_cache_read('ext_ip', 300);
+    if ($extData) {
+        $extIp = $extData['ip'] ?? '';
     } else {
         $fetched = trim(shell_exec('curl -sf --max-time 4 https://ifconfig.me 2>/dev/null') ?: '');
         if (preg_match('/^\d+\.\d+\.\d+\.\d+$/', $fetched)) {
             $extIp = $fetched;
-            file_put_contents($extIpCache, $extIp);
+            vv_cache_write('ext_ip', ['ip' => $extIp]);
         }
     }