refactor(telegram): separate bridge detail headers

[LimiNode]

What changed

Move Telegram bridge implementation-oriented headers into the family detail directory:

• TelegramSignalParser.hpp;
• TelegramWorkerMessageSource.hpp.

Keep public DTO, bridge, and bridge configuration headers at the Telegram family root. The public bridges/telegram.hpp aggregate still exposes the same namespaces and types, while internal header paths now match the layout used by other bridge families.

Compatibility

No class, namespace, DTO, or aggregate include API changes. Consumers should continue including optionx_cpp/bridges/telegram.hpp.

Validation

• telegram DTO tests: 4/4;
• telegram parser tests: 18/18;
• telegram bridge tests: 3/3;
• Telegram worker source tests: 2/2;
• telegram_signal_bridge_smoke: passed;
• telegram_archive_parser_smoke: passed;
• telegram_live_bridge_smoke: rebuilt successfully;
• git diff --check: passed.

This is a stacked cleanup PR based on chore/pin-tg-client-stdio-merge (optionx_cpp#136).