Add test suite (63 tests) and CI workflow, fix Settings API bugs

Test suite covering all three layers:

Python backend (25 tests):
- AppController: state machine, start/stop, callbacks, settings reload
- API server: REST endpoints, config CRUD, status, devices
- Config: dot-notation get/set, persistence, nested paths
- Main headless: ready event port format validation

Svelte frontend (14 tests via Vitest):
- Backend store: exported properties/methods, port derivation, URLs
- Config store: method names (fetchConfig not loadConfig), defaults
- Transcriptions store: add/clear/plaintext
- File extension regression: ensures $state runes only in .svelte.ts

Rust sidecar (24 tests via cargo test):
- Platform/arch detection, asset name construction
- Ready event deserialization (with extra fields tolerance)
- Path construction, version read/write, old version cleanup
- Zip extraction, SidecarManager lifecycle

CI workflow (.gitea/workflows/test.yml):
- Runs on push to main and PRs
- Three parallel jobs: Python, Frontend, Rust

Also fixes three bugs found during test planning:
- Settings: /api/check-updates -> GET /api/check-update
- Settings: /api/remote/login -> /api/login
- Settings: /api/remote/register -> /api/register

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/tests/test_api_server.py

@@ -0,0 +1,150 @@
+"""Tests for backend.api_server.APIServer REST endpoints."""
+
+import sys
+from pathlib import Path
+from unittest.mock import MagicMock, patch
+
+import pytest
+import pytest_asyncio
+
+# Ensure project root is on path
+project_root = Path(__file__).resolve().parent.parent.parent
+sys.path.insert(0, str(project_root))
+
+
+# ── GET /api/status ─────────────────────────────────────────────────
+
+
+@pytest.mark.asyncio
+async def test_get_status(api_client):
+    resp = await api_client.get("/api/status")
+    assert resp.status_code == 200
+    data = resp.json()
+    assert "state" in data
+    assert "is_transcribing" in data
+    assert "version" in data
+    assert "web_server" in data
+
+
+# ── GET /api/config ─────────────────────────────────────────────────
+
+
+@pytest.mark.asyncio
+async def test_get_config(api_client):
+    resp = await api_client.get("/api/config")
+    assert resp.status_code == 200
+    data = resp.json()
+    # The config should be a dict (the raw config mapping)
+    assert isinstance(data, dict)
+
+
+# ── PUT /api/config ─────────────────────────────────────────────────
+
+
+@pytest.mark.asyncio
+async def test_put_config(api_client, controller):
+    """Updating config via PUT should persist and return success."""
+    # Patch reload_engine to avoid heavy lifting
+    controller.reload_engine = MagicMock(return_value=(True, "ok"))
+    controller.current_model_size = "base.en"
+    controller.current_device_config = "auto"
+    controller.config.set("transcription.model", "base.en")
+    controller.config.set("transcription.device", "auto")
+
+    resp = await api_client.put(
+        "/api/config",
+        json={"settings": {"display.font_size": 24}},
+    )
+    assert resp.status_code == 200
+    body = resp.json()
+    assert body["status"] == "ok"
+
+    # Verify the value was actually saved
+    assert controller.config.get("display.font_size") == 24
+
+
+# ── POST /api/start (engine not ready) ─────────────────────────────
+
+
+@pytest.mark.asyncio
+async def test_start_when_not_ready(api_client, controller):
+    """Starting transcription without an engine should return 400."""
+    controller.transcription_engine = None
+    resp = await api_client.post("/api/start")
+    assert resp.status_code == 400
+
+
+# ── POST /api/clear ─────────────────────────────────────────────────
+
+
+@pytest.mark.asyncio
+async def test_clear(api_client, controller):
+    from client.transcription_engine_realtime import TranscriptionResult
+    from datetime import datetime
+
+    controller.transcriptions = [
+        TranscriptionResult(text="One", is_final=True, timestamp=datetime.now(), user_name="U"),
+    ]
+
+    resp = await api_client.post("/api/clear")
+    assert resp.status_code == 200
+    body = resp.json()
+    assert body["cleared"] == 1
+    assert len(controller.transcriptions) == 0
+
+
+# ── GET /api/audio-devices ──────────────────────────────────────────
+
+
+@pytest.mark.asyncio
+async def test_get_audio_devices(api_client, controller):
+    """Audio devices endpoint should return a list, even when mocked."""
+    # Mock sounddevice so the test works without audio hardware
+    with patch("backend.app_controller.AppController.get_audio_devices",
+               return_value=[{"index": 0, "name": "Mock Mic"}]):
+        resp = await api_client.get("/api/audio-devices")
+    assert resp.status_code == 200
+    data = resp.json()
+    assert "devices" in data
+    assert len(data["devices"]) >= 1
+
+
+# ── GET /api/compute-devices ────────────────────────────────────────
+
+
+@pytest.mark.asyncio
+async def test_get_compute_devices(api_client, controller):
+    resp = await api_client.get("/api/compute-devices")
+    assert resp.status_code == 200
+    data = resp.json()
+    assert "devices" in data
+    # At minimum we get the "Auto-detect" entry
+    assert any(d["id"] == "auto" for d in data["devices"])
+
+
+# ── GET /api/check-update ──────────────────────────────────────────
+
+
+@pytest.mark.asyncio
+async def test_check_update(api_client, controller):
+    """check-update should return a dict with an 'available' key."""
+    with patch.object(controller, "check_for_updates",
+                      return_value={"available": False, "current_version": "1.0.0"}):
+        resp = await api_client.get("/api/check-update")
+    assert resp.status_code == 200
+    data = resp.json()
+    assert "available" in data
+
+
+# ── GET /api/version ────────────────────────────────────────────────
+
+
+@pytest.mark.asyncio
+async def test_version(api_client):
+    resp = await api_client.get("/api/version")
+    assert resp.status_code == 200
+    data = resp.json()
+    assert "version" in data
+    # Should be a non-empty string
+    assert isinstance(data["version"], str)
+    assert len(data["version"]) > 0