feat: bounded pre-gen, cancellation, disk cache pruning, GPU lock

refactor: runtime config, Q&A flow module, storage paths, and cleanup

feat: persist voice profiles to Voice_Profile/ with auto-load on startup

test: add comprehensive integration test suite (74 tests)

perf: add TTS latency optimizations

feat: implement real voice cloning with Qwen3-TTS (sprint step 3)

feat: wire Whisper-small ASR and Qwen2.5-3B Q&A into app (sprint steps 9-10)

feat: integrate Supertonic TTS with sentence-level chunk streaming