Allow key verification to work for unknown nodes. (#10669)

* Allow key verification to work for unknown nodes.

* trunk

* More reliable admin key decryption

* Add admin key fallback tests

* Actually check haveRemoteKey

* Logging cleanup

* Address review feedback

- Persist the committed key + manually-verified flag in
  commitVerifiedRemoteNode via saveToDisk(SEGMENT_NODEDATABASE),
  replacing the "todo: initiate save"
- Guard the CryptoEngine pending-key slot with a dedicated internal
  lock; the Router reads it while already holding the non-recursive
  cryptLock, so the accessors cannot reuse that lock
- Draw the security number from the hardware RNG (CryptRNG fallback)
  under cryptLock instead of random(); on nRF52 the entropy fill
  toggles the same CC310 the BLE task's packet crypto uses
- Return true after fully handling the hash2 response (restores
  develop behavior; consistent with the hash1 branch)
- Take uint32_t in the number-picker callbacks so 8-digit hex
  nodenums can't truncate through int
- Trim over-long comments flagged by review

* feat(tests): add deterministic tests for admin session-key behavior

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Co-authored-by: Ben Meadors <benmmeadors@gmail.com>

test/support/AdminModuleTestShim.h

@@ -7,9 +7,11 @@
 class AdminModuleTestShim : public AdminModule
 {
   public:
+    using AdminModule::checkPassKey; // session-key gate seam (see test_admin_session_repro)
     using AdminModule::handleReceivedProtobuf;
     using AdminModule::handleSetConfig;
     using AdminModule::handleSetModuleConfig;
+    using AdminModule::setPassKey;
 
     // With an "open edit transaction" saveChanges() is a pure no-op: no reloadConfig/saveToDisk/reboot.
     void deferSaves() { hasOpenEditTransaction = true; }