feat(web): support list editing for channel array fields

[wj-xiao]

📝 Description

This PR improves channel configuration editing for array/list fields in the launcher web console.

It adds chip-style list editing for channel array values, including allow_from, allow_origins, group trigger prefixes, and other channel-specific string array settings. The backend now normalizes string, numeric, and array payloads for these fields before saving config patches, so pasted comma/newline-separated values are stored consistently and empty entries are not persisted.

🗣️ Type of Change

• 🐞 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 📖 Documentation update
• ⚡ Code refactoring (no functional changes, no api changes)

🤖 AI Code Generation

• 🤖 Fully AI-generated (100% AI, 0% Human)
• 🛠️ Mostly AI-generated (AI draft, Human verified/modified)
• 👨‍💻 Mostly Human-written (Human lead, AI assisted or none)

🔗 Related Issue

N/A

📚 Technical Context (Skip for Docs)

• Reference URL: N/A
• Reasoning: Channel array fields were previously edited as comma-separated text, which made it easy to leave accidental whitespace, duplicates, hidden characters, or pending draft text out of the saved payload. This change keeps the UI list-oriented while retaining backend compatibility for string and numeric payloads.

🧪 Test Environment

• Hardware: Apple Silicon Mac
• OS: macOS 26.4.1
• Model/Provider: N/A
• Channels: Telegram, Discord, Slack, Feishu, Weixin, WeCom, Pico, IRC

📸 Evidence (Optional)

Click to view Logs/Screenshots

go test -tags goolm,stdjson ./pkg/config ./web/backend/api
ok  	github.com/sipeed/picoclaw/pkg/config	2.302s
ok  	github.com/sipeed/picoclaw/web/backend/api	11.250s

pnpm lint
> picoclaw-web@0.0.0 lint /Users/xiao/github/wj-xiao/picoclaw/web/frontend
> eslint .

☑️ Checklist

• My code/docs follow the style of this project.
• I have performed a self-review of my own changes.
• I have updated the documentation accordingly.