feat: Add GL.iNet router support with supplementary API data

[diggerburg]

Summary

GL.iNet routers run a custom firmware layer on top of OpenWrt that provides additional data not available through standard ubus/LuCI RPCs. This PR auto-detects GL.iNet routers and fetches supplementary data from their /rpc JSON-RPC API alongside the existing LuCI data path.

All changes are backward-compatible — GL.iNet-specific code only activates when the router model contains "GL-" or "GL.iNet". Non-GL.iNet routers are completely unaffected.

What's new

Dashboard:

• CPU temperature display (GL.iNet routers report SoC temperature)
• Fan status (speed/active for models with fans)
• CPU load shown as percentage on GL.iNet (core count is known), load average on other routers
• WiFi cards show band labels (2.4 GHz / 5 GHz / 6 GHz)

Clients:

• Accurate online/offline status from GL.iNet API (standard ubus DHCP leases don't distinguish)
• WiFi band per client (2.4 GHz / 5 GHz / 6 GHz) instead of generic "Wi-Fi" / "Unknown"
• Device class enrichment (phone, laptop, etc.)
• Better device names from GL.iNet's client database
• Online clients sorted before offline

Interfaces:

• Real WiFi channels on Qualcomm IPQ platforms (where iwinfo returns N/A through ubus)
• WiFi band labels in subtitle (e.g., "AP • 5 GHz • Ch. 44")
• Tailscale interface shows actual IP address (Tailscale manages IPs outside netifd)

Bug fix:

• CPU load no longer shows 100% on multi-core routers. The previous formula (load[0] / 65536) * 100 treated load average as a percentage, but load average of 2.0 on a 4-core system is ~50% utilization, not 200% clamped to 100%.

Screenshots

Dashboard	Clients	Interfaces

Technical details

• GlInetApiService — lightweight service for GL.iNet /rpc auth + data fetching
• Sha256Crypt — Unix SHA-256 crypt implementation (GL.iNet firmware ≥4.x uses $5$ password hashing)
• GL.iNet session is cached and reused across poll cycles (cleared on logout/router switch)
• HttpClientManager is injected (shared certificate acceptance with main LuCI client)
• formatWifiBand() utility extracted to avoid duplication

Testing

• 8 unit tests for SHA-256 crypt (verified against passlib reference vectors including empty password, unicode, special chars, custom rounds)
• 6 unit tests for GlInetApiService (auth state, session cleanup, graceful null returns)
• All 27 existing tests continue to pass
• 41 total tests, 0 analyzer warnings
• Tested on real hardware: GL.iNet GL-BE9300 (Flint 3), firmware 4.8.4, via LAN and Tailscale

Checklist

• Code follows Dart style guide (dart format applied)
• flutter analyze passes (0 errors, 0 warnings)
• flutter test passes (41/41)
• Backward compatible with non-GL.iNet OpenWrt routers
• No security vulnerabilities (password hashed locally, never logged)
• Documentation in code comments for GL.iNet auth protocol