Fix storage recovery and deferred runtime state

Recover usable ESP32 preferences and channels before permitting replacement; keep identity and ACL persistence transactional and complete.

Preserve MQTT commit boundaries, restore OTA identity and policy after deferred allocation, retain radio gain retries, and reject invalid flood limits. Add production-path fault regressions and CI coverage.

src/helpers/ContactFileTransaction.h

@@ -10,6 +10,9 @@
 
 namespace mesh {
 class ContactFileTransaction {
+public:
+  using PresenceProbe = bool (*)(FILESYSTEM*, const char*, bool&);
+private:
   FILESYSTEM* _fs;
   const char* _target;
   char _temp[48];
@@ -19,17 +22,30 @@ class ContactFileTransaction {
   uint32_t _crc = 0xffffffff;
   bool _ok = false;
   bool _finished = false;
+  PresenceProbe _presence;
+  static bool probe(FILESYSTEM* fs, const char* path, bool& present,
+                    PresenceProbe presence) {
+    if (presence) return presence(fs, path, present);
+    present = fs->exists(path);
+    return true;
+  }
 public:
-  static bool recover(FILESYSTEM* fs, const char* target) {
+  static bool recover(FILESYSTEM* fs, const char* target,
+                      PresenceProbe presence = nullptr) {
     char backup[48];
     snprintf(backup, sizeof(backup), "%s.bak", target);
-    if (fs->exists(target)) return true;
-    return !fs->exists(backup) || fs->rename(backup, target);
+    bool target_exists = false, backup_exists = false;
+    if (!probe(fs, target, target_exists, presence)
+        || !probe(fs, backup, backup_exists, presence)) return false;
+    if (target_exists) return true;
+    return !backup_exists || fs->rename(backup, target);
   }
-  ContactFileTransaction(FILESYSTEM* fs, const char* target) : _fs(fs), _target(target) {
+  ContactFileTransaction(FILESYSTEM* fs, const char* target,
+                         PresenceProbe presence = nullptr)
+      : _fs(fs), _target(target), _presence(presence) {
     snprintf(_temp, sizeof(_temp), "%s.tmp", target);
     snprintf(_backup, sizeof(_backup), "%s.bak", target);
-    if (!recover(fs, target)) return;
+    if (!recover(fs, target, presence)) return;
     if (fs->exists(_temp) && !fs->remove(_temp)) return;
 #if defined(RP2040_PLATFORM)
     _file = fs->open(_temp, "w");
@@ -67,9 +83,12 @@ public:
     }
     if (verify) verify.close();
     ok = ok && crc == _crc;
-    if (ok && _fs->exists(_backup)) ok = _fs->remove(_backup);
+    bool backup_exists = false, target_exists = false;
+    if (ok) ok = probe(_fs, _backup, backup_exists, _presence)
+        && probe(_fs, _target, target_exists, _presence);
+    if (ok && backup_exists) ok = _fs->remove(_backup);
     bool backed_up = false;
-    if (ok && _fs->exists(_target)) {
+    if (ok && target_exists) {
       ok = _fs->rename(_target, _backup);
       backed_up = ok;
     }