refactor: Dedupe wifi scan in-place without std::map (#2262)

## Summary

`std::map` heap-allocates each node. Avoid using it for wifi SSID
dedupe, and instead just dedupe in-place with the existing `networks`
vector. Removed dead `ipAddress` member in `WifiNetworkInfo` struct.

---

### AI Usage

Did you use AI tools to help write this code? _**PARTIALLY**_

src/activities/network/WifiSelectionActivity.cpp

@@ -6,8 +6,6 @@
 #include <Logging.h>
 #include <WiFi.h>
 
-#include <map>
-
 #include "CrossPointSettings.h"
 #include "MappedInputManager.h"
 #include "WifiCredentialStore.h"
@@ -118,39 +116,35 @@ void WifiSelectionActivity::processWifiScanResults() {
     return;
   }
 
-  // Scan complete, process results
-  // Use a map to deduplicate networks by SSID, keeping the strongest signal
-  std::map<std::string, WifiNetworkInfo> uniqueNetworks;
+  // Scan complete, process results — deduplicate in-place, keeping strongest signal
+  networks.clear();
+  networks.reserve(scanResult);
 
   for (int i = 0; i < scanResult; i++) {
-    std::string ssid = WiFi.SSID(i).c_str();
+    char ssid[33];
+    strlcpy(ssid, WiFi.SSID(i).c_str(), sizeof(ssid));
     const int32_t rssi = WiFi.RSSI(i);
 
     // Skip hidden networks (empty SSID)
-    if (ssid.empty()) {
+    if (ssid[0] == '\0') {
       continue;
     }
 
-    // Check if we've already seen this SSID
-    auto it = uniqueNetworks.find(ssid);
-    if (it == uniqueNetworks.end() || rssi > it->second.rssi) {
-      // New network or stronger signal than existing entry
+    auto it =
+        std::find_if(networks.begin(), networks.end(), [&ssid](const WifiNetworkInfo& n) { return n.ssid == ssid; });
+    if (it == networks.end()) {
       WifiNetworkInfo network;
       network.ssid = ssid;
       network.rssi = rssi;
       network.isEncrypted = (WiFi.encryptionType(i) != WIFI_AUTH_OPEN);
       network.hasSavedPassword = WIFI_STORE.hasSavedCredential(network.ssid);
-      uniqueNetworks[ssid] = network;
+      networks.push_back(std::move(network));
+    } else if (rssi > it->rssi) {
+      it->rssi = rssi;
+      it->isEncrypted = (WiFi.encryptionType(i) != WIFI_AUTH_OPEN);
     }
   }
 
-  // Convert map to vector
-  networks.clear();
-  for (const auto& pair : uniqueNetworks) {
-    // cppcheck-suppress useStlAlgorithm
-    networks.push_back(pair.second);
-  }
-
   // Sort: saved-password networks first, then by signal strength (strongest first)
   std::sort(networks.begin(), networks.end(), [](const WifiNetworkInfo& a, const WifiNetworkInfo& b) {
     if (a.hasSavedPassword != b.hasSavedPassword) {

src/activities/network/WifiSelectionActivity.h

@@ -18,7 +18,6 @@ struct WifiNetworkInfo {
   int32_t rssi;
   bool isEncrypted;
   bool hasSavedPassword;  // Whether we have saved credentials for this network
-  std::string ipAddress;  // Populated after connection for display
 };
 
 // WiFi selection states