Phase 4.7b: Extract service init + remove globals (#581)

[shikhalev]

Summary

• All inline service initialization extracted from startup_event() into domain startup.py modules:
  • modules/speech/startup.py — init_tts_services(), init_stt_service(), init_streaming_tts_manager()
  • modules/llm/startup.py — init_llm_service() (full fallback chain), create_llm_switch_callback() (InternetMonitor callback factory)
  • modules/knowledge/startup.py — init_wiki_rag() (tiered embedding provider + task registration)
  • modules/core/startup.py — init_internet_monitor(), check_legacy_files(), graceful_shutdown()
  • modules/telephony/startup.py — init_gsm_services() (GSM + voice calls)
• 8 global service variables removed from orchestrator.py (voice_service, anna_voice_service, piper_service, openvoice_service, stt_service, llm_service, streaming_tts_manager, current_voice_config)
• ServiceContainer (app/dependencies.py) is now the single source of truth — no more dual state
• _switch_llm callback refactored: closure factory in modules/llm/startup.py, writes only to container.llm_service + os.environ["LLM_BACKEND"] (no globals)
• Optional imports (VLLM_AVAILABLE, PIPER_AVAILABLE, etc.) moved to domain startup modules
• orchestrator.py: 805 → 321 lines (−60%) — pure wiring, zero domain logic

Test plan

• ruff check . — all checks passed
• ruff format — formatted
• pytest tests/ — 65 tests passed
• Manual: Docker deploy + curl /health
• Manual: verify bot auto-start, LLM init, FAQ/presets reload
• Manual: verify InternetMonitor callback (if applicable)

Closes #581

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