refactor: drop trezord-go bridge, keep only node-bridge

[mroz22]

Summary

• Removes legacy trezord-go binaries (2.0.32 / 2.0.33, x86 + ARM) and all related code paths.
• Bridge support now consists exclusively of node-bridge and local-suite-node-bridge.
• Cleans up Dockerfile, Nix entrypoint, .gitignore / .dockerignore, docs (README, MCP, controller, development), MCP tool docstring, controller integration tests, and dashboard (drops legacy/modern grouping).

Rationale

trezord-go is no longer supported by Trezor Suite. This PR is the final step that removes it.

The first step — adding a UI warning while keeping trezord-go available for older-Suite testing — is #385. Merge that first; this one can land later once we are comfortable retiring legacy entirely.

Notable code changes

• src/bridge.py: drop trezord-go branch in get_command_list, remove ARM-suffix logic and is_node_bridge_running.
• src/binaries.py: drop BRIDGE_BIN_DIR and legacy bridge entries in explore_bridges().
• src/emulator.py: get_device() always uses UDP (node bridge).
• src/binaries/trezord-go/: directory removed.
• tests/controller_test.py: BRIDGE_TO_TEST = "node-bridge".

Test plan

• CI build passes
• Docker image builds without trezord-go download step
• bridge-start with node-bridge works from dashboard, controller WS, and MCP
• bridge-start with an unknown version returns a structured failure
• Emulator start/stop with bridge running still works (UDP path)