[client] Add block inbound flag to disallow inbound connections of any kind

[lixmal]

Describe your changes

This option prevents adding any inbound rules (peer + route ACLs) and ssh

Issue ticket number and link

Stack

Checklist

• Is it a bug fix
• Is a typo/documentation fix
• Is a feature enhancement
• It is a refactor
• Created tests that fail without the change (if possible)
• Extended the README / documentation, if necessary

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[Copilot]

Pull Request Overview

This PR adds a block inbound flag to disallow inbound connections and propagates that flag through the UI, configuration, protocol definitions, and firewall logic.

• Added a new "Block Inbound Connections" option in the client UI with corresponding label and description changes.
• Updated configuration, proto messages, and engine logic to support blocking inbound connections.
• Modified command-line flags and login request setup to incorporate the new block inbound functionality.

Reviewed Changes

Copilot reviewed 17 out of 17 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
client/ui/const.go	Updated menu description strings and added block inbound menu text.
client/ui/client_ui.go	Added the block inbound checkbox and updated configuration update logic.
client/server/server.go	Propagated the new block inbound flag in login requests and config responses.
client/proto/daemon.proto	Introduced new proto fields for block inbound connections.
client/internal/engine.go	Adjusted firewall and SSH server initialization logic using BlockInbound.
client/internal/connect.go	Integrated block inbound flag into engine configuration and login request.
client/internal/config.go	Added BlockInbound field in configuration and updated its application logic.
client/internal/acl/manager.go	Removed duplicate firewall nil check since it's already handled earlier.
client/firewall/*	Updated IP forwarding and nat rule management to reflect block inbound changes.
client/cmd/*	Introduced new command-line flags for block inbound and updated config setup.

Comments suppressed due to low confidence (2)

client/cmd/up.go:263

• The function runInForegroundMode returns only an error. Change 'return nil, err' to 'return err' to match the function signature.

return nil, err

client/cmd/up.go:361

• The function runInDaemonMode returns only an error. Change 'return nil, err' to 'return err' to adhere to the expected signature.

return nil, err

[sonarqubecloud]

Quality Gate failed

Failed conditions
9.9% Duplication on New Code (required ≤ 5%)

See analysis details on SonarQube Cloud