fix: enforce link relay input permissions

[NeerajCodz]

Motivation

• The link relay path allowed approved sessions (including view_only or approve_only) to send terminal input, bypassing the intended access-mode approval shown to desktop users.
• Relay messages and desktop relay handling did not validate the approved mode or reliably verify the session_id/terminal mapping before writing to the PTY, creating an authorization bypass.

Description

• Require that a relay websocket session is approved before registering the client by checking session.status in apis/link/src/relay.ts during relay.auth processing.
• Persist the approved mode on the relay Client and reject mobile relay.message frames with direction === "input" unless client.mode === "full_control" in apis/link/src/relay.ts.
• Add LinkManager::session_allows_terminal_input in crates/orphix-core/src/link/mod.rs to verify the inbound session_id matches the stored desktop session, the stored mode is full_control, and the relay mapping points the session to the terminal before accepting input.
• Apply the desktop-side authorization check in the LinkMessage::RelayMessage branch to deny unauthorized input before any RPC handling or TerminalManager::write occurs.

Testing

• Ran cargo check -p orphix-core which completed successfully.
• Ran bunx prettier --check apis/link/src/relay.ts which passed formatting checks after applying changes.
• Attempted to build the link API with bun --filter @orphix/link-api build but the TypeScript build failed in this environment due to missing/resolvable dev/peer dependencies and type packages (e.g. fastify, ws, jose, @types/node, @orphix/encryption), so a full API build could not be completed here.

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Codex Task