Update docs and screenshots

backend/tests/test_bpm_service.py

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+from __future__ import annotations
+
+import asyncio
+
+from app.bpm.service import BeatAnalyzer, BpmService
+
+
+def test_beat_analyzer_estimates_click_track_bpm() -> None:
+    analyzer = BeatAnalyzer(sample_rate=44_100, window_size=1024)
+    click = (b"\x00\x40" * 2048) + (b"\x00\x00" * (44_100 // 2 - 2048))
+
+    result = None
+    for _ in range(6):
+        result = analyzer.feed_pcm16(click)
+
+    assert result is not None
+    bpm, confidence = result
+    assert 117 <= bpm <= 124
+    assert confidence > 0.5
+
+
+def test_bpm_service_synthetic_audio_updates_snapshot() -> None:
+    async def run_test() -> None:
+        service = BpmService()
+        await service.start_audio("synthetic-click-track")
+        await asyncio.sleep(1.2)
+        snapshot = service.snapshot()
+        await service.stop_audio()
+
+        assert snapshot["mode"] == "audio:synthetic-click-track"
+        assert snapshot["audio_connected"] is True
+        assert 117 <= float(snapshot["bpm"]) <= 123
+        assert float(snapshot["confidence"]) > 0.3
+        assert float(snapshot["input_level"]) > 0.0
+        assert float(snapshot["peak_level"]) >= float(snapshot["input_level"])
+        assert snapshot["clipping"] is False
+
+    asyncio.run(run_test())
+
+
+def test_parse_alsa_card_line_supports_named_aliases() -> None:
+    service = BpmService()
+
+    card = service._parse_card_line("card 1: SB [HDA ATI SB], device 0: ALC883 Analog [ALC883 Analog]")
+    device = service._parse_device_from_card_line(
+        "card 1: SB [HDA ATI SB], device 0: ALC883 Analog [ALC883 Analog]"
+    )
+
+    assert card == ("1", "SB", "HDA ATI SB")
+    assert device == ("0", "ALC883 Analog", "ALC883 Analog")
+
+
+def test_busy_alsa_error_is_humanized() -> None:
+    service = BpmService()
+
+    message = service._humanize_alsa_error(
+        "alsa:plughw:CARD=SB,DEV=0",
+        "arecord: main:831: audio open error: Device or resource busy",
+    )
+
+    assert "Mikrofonen er optaget" in message