Fix heap memory leak and reporting of saved Wi-Fi networks

[JanPetterMG]

This pull request addresses various bugs related to Wi-Fi network reporting and improves the NVS (Non-Volatile Storage) handling logic, enhancing overall connectivity reliability.

Key changes

• Fixed reporting of saved Wi-Fi networks.
• Resolved a memory leak in NVS handle management.
• Refactored NVS logic for better clarity and performance.
• Refactored IP address logging for better clarity
• Updated code styling for consistency.

Impact

These changes improve the stability and performance of the connectivity service, ensuring more reliable Wi-Fi network management. Users may experience fewer issues, and the codebase becomes easier to maintain for contributors.

[Copilot]

Pull request overview

This PR improves Wi‑Fi connectivity reporting across the firmware and webapp by fixing how saved networks are read/transmitted and by tightening NVS handle usage to avoid leaks during NVS operations.

Changes:

• Firmware: Refactors NVS read/write flows (country code + Wi‑Fi credential blob) to ensure nvs_close() is consistently called and to correct saved-network reporting.
• Firmware: Renames the internal mDNS state flag (mDNS → mdns) and applies some type/style cleanups (e.g., 53U, 80U, brace-init).
• Webapp: Minor UI behavior tweak when selecting SSIDs in the sidebar.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
webapp/src/services/Connectivity.tsx	Adjusts sidebar selection behavior for small viewports.
firmware/src/services/ConnectivityService.cpp	Refactors NVS interactions, improves saved-network reporting, and applies several style/type adjustments.
firmware/include/services/ConnectivityService.h	Renames mDNS state field and modernizes member initialization.

Comments suppressed due to low confidence (1)

firmware/src/services/ConnectivityService.cpp:220

• WiFi.globalIPv6().toString() returns a temporary String; taking c_str() into a const char* leaves ipv6 pointing at freed storage immediately after the full-expression. This can make the strcmp/log read invalid memory. Store the String first (or copy into a stable buffer) and use c_str() from that stable object.

    const char *const ipv6{WiFi.globalIPv6().toString().c_str()};
    if (strcmp(ipv6, "") != 0)
    {
        ESP_LOGI("Wi-Fi", "IPv6 %s", ipv6); // NOLINT(cppcoreguidelines-pro-type-vararg,hicpp-vararg)
        if (!Connectivity.routable)

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.