Add IPv6 support for WiFi and Ethernet interfaces

[Copilot]

IPv6 Support Implementation - Build Fixes Applied ✓

Build Error Fixes

• Fix WiFi.enableIPv6() → WiFi.enableIpV6() (correct case)
• Fix WiFi.linkLocalIPv6() → WiFi.localIPv6() (correct method)
• Fix ETH.enableIPv6() → ETH.enableIpV6() (correct case)
• Fix ETH.linkLocalIPv6() → ETH.localIPv6() (correct method)

Original Implementation

• Add IPv6 address storage to NetManagerTask class (net_manager.h)
• Add public getIpv6() method to expose IPv6 address
• Enable IPv6 for WiFi via WiFi.enableIpV6() in wifiClientConnect()
• Enable IPv6 for Ethernet via ETH.enableIpV6() when connected
• Add ARDUINO_EVENT_WIFI_STA_GOT_IP6 event handler
• Add ARDUINO_EVENT_ETH_GOT_IP6 event handler
• Update web server API to include ipv6address field
• Address code review feedback on event patterns
• Fix JSON buffer size (increased to 256 bytes)
• Pass CodeQL security analysis

Technical Details

• Uses localIPv6() to retrieve link-local IPv6 addresses
• WiFi handler emits status event (matches IPv4 pattern)
• Ethernet handler stores address only (matches IPv4 pattern)
• Backward compatible - IPv4 unchanged
• Empty string if IPv6 unavailable

API Response

{
  "ipaddress": "192.168.1.100",
  "ipv6address": "fe80::1234:5678:90ab:cdef",
  "macaddress": "AA:BB:CC:DD:EE:FF"
}

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Feature Request: IPv6 support</issue_title>
<issue_description>Hello,

I prefer to use IPv6 where possible. My ESP32-Faikin module supports it.
Is it something that could be added to OpenEVSE?

Thanks,

nick.
</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Feature Request: IPv6 support #793

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[github-actions]

Test Results

58 tests  ±0   58 ✅ ±0   1s ⏱️ ±0s
 1 suites ±0    0 💤 ±0 
 1 files   ±0    0 ❌ ±0 

Results for commit 5d71913. ± Comparison against base commit d3c4626.

♻️ This comment has been updated with latest results.

[jeremypoulter]

@copilot there are build errors from the workflow, please check and resolve the issues

[Copilot]

@copilot there are build errors from the workflow, please check and resolve the issues

Fixed the build errors in commit 5d71913. The issue was incorrect method name capitalization - ESP32 Arduino core uses enableIpV6() and localIPv6() (not enableIPv6() and linkLocalIPv6()). All builds should now pass.