fix(web): implement delete_cached so the font catalog cache actually invalidates

api_v3.py's font upload/delete handlers import delete_cached from
web_interface.cache, but the function was never defined. The surrounding
except ImportError silently swallowed the failure, so the fonts_catalog
cache entry survived uploads/deletes and newly uploaded fonts did not
appear until the TTL expired or the service restarted.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SXb4mKcAkVaxkeTb3YnAdr

test/web_interface/test_cache.py

@@ -0,0 +1,38 @@
+"""Tests for the web interface's in-memory cache helpers."""
+import pytest
+
+from web_interface.cache import delete_cached, get_cached, invalidate_cache, set_cached
+
+
+@pytest.fixture(autouse=True)
+def clean_cache():
+    invalidate_cache()
+    yield
+    invalidate_cache()
+
+
+def test_set_and_get():
+    set_cached('key', 'value')
+    assert get_cached('key') == 'value'
+
+
+def test_get_missing_returns_none():
+    assert get_cached('missing') is None
+
+
+def test_delete_cached_removes_key():
+    set_cached('fonts_catalog', ['a-font'])
+    delete_cached('fonts_catalog')
+    assert get_cached('fonts_catalog') is None
+
+
+def test_delete_cached_missing_key_is_noop():
+    delete_cached('never-set')  # must not raise
+
+
+def test_invalidate_cache_pattern():
+    set_cached('fonts_catalog', 1)
+    set_cached('plugins_list', 2)
+    invalidate_cache('fonts')
+    assert get_cached('fonts_catalog') is None
+    assert get_cached('plugins_list') == 2

web_interface/cache.py

@@ -29,6 +29,12 @@ def set_cached(key: str, value: Any, ttl_seconds: int = 60) -> None:
     _cache_timestamps[key] = time.time()
 
 
+def delete_cached(key: str) -> None:
+    """Remove a single key from the cache if present."""
+    _cache.pop(key, None)
+    _cache_timestamps.pop(key, None)
+
+
 def invalidate_cache(pattern: Optional[str] = None) -> None:
     """Invalidate cache entries matching pattern, or all if pattern is None."""
     if pattern is None: