docs: add SetupService to architecture, update changelog and testing docs

- ARCHITECTURE.md: add setup_service.py to services list
- CHANGELOG.md: add Unreleased section with folder scan key resolution fix
- TESTING.md: add SetupService testing section with example tests

docs/ARCHITECTURE.md

@@ -81,6 +81,7 @@ src/server/
 |   +-- websocket_service.py# WebSocket broadcasting
 |   +-- queue_repository.py # Database persistence
 |   +-- nfo_service.py      # NFO metadata management
+|   +-- setup_service.py    # Series key resolution from folder names
 |   +-- folder_scan_service.py # Daily folder maintenance scan
 +-- models/                 # Pydantic models
 |   +-- auth.py             # Auth request/response models

docs/CHANGELOG.md

@@ -37,6 +37,17 @@ This changelog follows [Keep a Changelog](https://keepachangelog.com/) principle
 
 ---
 
+## [Unreleased] - 2026-06-05
+
+### Fixed
+
+- **Folder scan series key resolution**: Fixed "Could not resolve series key for folder, skipping" warnings during library setup. `_resolve_key_via_search()` now uses fuzzy title matching instead of exact string comparison.
+    - Added `_normalize_title()` to strip anime suffixes: `(TV)`, `(Anime)`, `(OAD)`, `(OVA)`, `(Special)`, `(Movie)`, `(Spin-Off)`
+    - Added `_titles_match()` using `difflib.SequenceMatcher` with 0.85 similarity threshold for tolerance of minor title variations
+    - Added debug logging for title mismatches and multiple search results
+
+---
+
 ## [1.3.1] - 2026-02-22
 
 ### Added

docs/TESTING.md

@@ -73,40 +73,31 @@ from src.server.models.download import DownloadItem, EpisodeIdentifier
 class MockQueueRepository:
     def __init__(self):
         self._items: Dict[str, DownloadItem] = {}
-
-    async def save_item(self, item: DownloadItem) -> DownloadItem:
-        self._items[item.id] = item
-        return item
-
-    async def get_item(self, item_id: str) -> Optional[DownloadItem]:
-        return self._items.get(item_id)
-
-    async def get_all_items(self) -> List[DownloadItem]:
-        return list(self._items.values())
-
-    async def set_error(self, item_id: str, error: str) -> bool:
-        if item_id in self._items:
-            self._items[item_id].error = error
-            return True
-        return False
-
-    async def delete_item(self, item_id: str) -> bool:
-        if item_id in self._items:
-            del self._items[item_id]
-            return True
-        return False
-
-    async def clear_all(self) -> int:
-        count = len(self._items)
-        self._items.clear()
-        return count
 ```
 
-**Key points:**
-- The mock uses in-memory storage, no database required
-- All async methods are implemented (even if just pass-through)
-- `save_item` uses `item.id` as key (must be set before calling)
-- Suitable for unit tests only (no persistence)
+### Testing SetupService
+
+SetupService handles series key resolution from folder names during library setup. Test file: `tests/unit/test_setup_service.py`.
+
+Key methods tested:
+- `_extract_year_from_folder_name()` — parses `(YYYY)` suffix
+- `_extract_title_from_folder_name()` — strips year suffix
+- `_resolve_key_via_search()` — resolves provider key via fuzzy title matching
+
+```python
+@pytest.mark.asyncio
+async def test_returns_key_when_single_exact_match(self):
+    """Search returns 1 result with same name → returns key."""
+    mock_series_app = AsyncMock()
+    mock_series_app.search.return_value = [
+        {'title': 'Attack on Titan', 'link': '/anime/stream/attack-on-titan'}
+    ]
+
+    with patch('src.server.services.setup_service.get_series_app', return_value=mock_series_app):
+        result = await SetupService._resolve_key_via_search("Attack on Titan")
+
+    assert result == 'attack-on-titan'
+```
 
 ### Mocking aiohttp Sessions