feat(KLEF): Add frontend_url support to plugin system

[NathanRoos]

Pull Request

Summary

• Adds frontend_url field to the plugin domain so frontend-only plugins can serve a JS bundle to the panel
• Exposes installed plugins via the admin API with frontend_url included so the panel knows where to load each plugin's script from
• Frontend-only plugins (no gRPC addr) are now treated as healthy/running instead of being marked as unreachable

Related Issues

Closes #

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Changes

What's Included

• internal/core/plugins/domain/plugin.go — adds FrontendURL field to plugin struct
• internal/core/plugins/adapters/persistence/store.go — reads/writes frontend_url column
• internal/core/plugins/adapters/http/handler.go — includes frontend_url in installed plugins response
• internal/core/plugins/application/manager.go — skips gRPC health check for plugins with no gRPC addr
• Dockerfile — resolves merge conflict, uses GOWORK=off go mod download consistent with build step

What's Not Included

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Testing

How Was This Tested?

Tested manually to see if the plugins worked

Test Coverage

• Unit tests added or updated
• Integration tests added or updated
• Manually tested end-to-end

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Breaking Changes

Does this PR introduce breaking changes?

• Yes
• No

If yes, describe the impact and any required migration steps:

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Security Considerations

• This PR affects authentication or authorization logic
• This PR touches secrets, tokens, or environment variables
• This PR affects infrastructure, deployment pipelines, or network configuration

If any box is checked, describe the security impact and any mitigations applied:

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Documentation

Does this PR require documentation updates?

• Yes
• No

If yes, check all that apply:

• README.md
• ARCHITECTURE.md
• API reference
• Architecture diagrams (C4 / DDD)
• /docs

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UI/UX (If Applicable)

• Includes new components or views
• Changes styles or theme tokens
• Responsive behavior verified
• Requires design approval

Screenshots or recordings:

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Pre-Merge Checklist

• PR title follows semantic format (feat:, fix:, chore:, docs:, refactor:, test:)
• All CI checks passing
• Code follows project style guidelines
• No debug logs or commented-out code left in
• Dependencies reviewed (no unnecessary additions)
• No sensitive information included

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Reviewer Notes