refactor: split types.py into device.py, net.py, and network/records.py

[kewde]

Summary

Stacked on #14 — targets that branch instead of master since it continues the same cleanup; merge #14 first, then retarget/merge this one.

types.py had become a grab-bag with three genuinely unrelated concerns living in one file with no clear ownership:

• knx_gui/device.py — the device/com-object domain model (Device, ComObject, ComObjectFlags, PinDir, PinRow, generate_rows, etc.). Kept together as one module rather than split further: Device.rows calls generate_rows/PinRow directly, so splitting those into plugins/node_editor/ would've made a top-level domain type depend on a specific UI plugin — the same backwards-dependency problem already being avoided elsewhere in this codebase.
• knx_gui/net.py — TelegramSource, the dispatch-chain source tag shared by connection/network/proxy/virtual. (Will end up alongside Peer once the in-progress pcap-capture branch merges — same category of thing, used by the same set of files.)
• knx_gui/plugins/network/records.py — CemiRecord, TelegramRecord. Exclusively consumed by the network plugin, so plugin-local scope fits.

Also removed is_default_flags/listen_obj/send_obj/bidirectional_obj — confirmed dead code (defined, never called anywhere in the app).

Test plan

• uv run ruff check / ruff format --check clean
• uv run pyright — 0 errors (note: doesn't actually cover apps/knx-gui, scoped to packages/* only)
• Direct import smoke test of all 19 touched modules — all import cleanly
• uv run pytest — 231 passed
• Launched the GUI — demo project loads with 5 devices, exercising the moved Device/ComObject code path directly