webauth-helper: add package

[Tokisaki-Galaxy]

📦 Package Details

Maintainer: @Tokisaki-Galaxy

Description:
This package provides a pure Rust-based WebAuthn/Passkey backend implementation for OpenWrt. It is designed to address the lack of modern authentication support in LuCI as discussed in openwrt/luci#8273

Key features:
Implements WebAuthn RP (Relying Party) logic for OpenWrt.
Lightweight and optimized for embedded systems (using Rust/Musl).
Provides the necessary backend API for LuCI to support Passkey login.

UPX COMPRESSION SUMMARY
==========================================
| Target                                   | Before (KB)  | After (KB)   | Ratio      |
| ---------------------------------------- | ------------ | ------------ | ---------- |
| aarch64-unknown-linux-musl               |        956 KB |        371 KB |     61.2% |
| arm-unknown-linux-musleabi               |       1090 KB |        412 KB |     62.2% |
| arm-unknown-linux-musleabihf             |       1086 KB |        411 KB |     62.1% |
| armv5te-unknown-linux-musleabi           |       1094 KB |        414 KB |     62.2% |
| armv7-unknown-linux-musleabi             |       1078 KB |        409 KB |     62.1% |
| armv7-unknown-linux-musleabihf           |       1058 KB |        412 KB |     61.0% |
| mips-unknown-linux-musl                  |       1395 KB |        452 KB |     67.6% |
| mipsel-unknown-linux-musl                |       1395 KB |        461 KB |     66.9% |
| powerpc64le-unknown-linux-musl           |       1220 KB |        429 KB |     64.8% |
| riscv64gc-unknown-linux-musl             |        961 KB |        399 KB |     58.4% |
| x86_64-unknown-linux-musl                |       1140 KB |        418 KB |     63.3% |
==========================================

https://github.com/Tokisaki-Galaxy/webauthn-helper/actions/runs/21793715110/job/62877699717

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🧪 Run Testing Details

• OpenWrt Version:23.05/24.10
• OpenWrt Target/Subtarget:multiarch
• OpenWrt Device:Docker(x86_64)/aarch(MT7981)

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✅ Formalities

• I have reviewed the CONTRIBUTING.md file for detailed contributing guidelines.