feat(diagnostics): the admin log console

Admin → Diagnostics reads the server's stored log: one list, newest first,
where a line opens in place to its full record (time, source and logger,
account, request and job ids, version, message, attributes, stack). A
request or job id narrows the list to that request or job with every other
filter off, shown as a removable chip. Filters: level group, source,
account, event, period and a free-text search; all of them live in the URL
(`l*` keys, which setPage clears like the Plex and Channels keys), so a
filtered view is a link and Back restores it. "Live" re-reads the newest
page every few seconds while the tab is visible; paging into older rows
turns it off. Copy puts the loaded lines on the clipboard as JSON lines.

The facet counts now honour every filter but their own, as the feed's do:
a request pivot narrows them, and a picked level does not zero its
siblings. A value in use stays offered even when the counts drop it.

"Saját napló" and the console draw a line with one shared component,
`LogLine`, whose phone layout gives the message its own full-width line
(sharing the code's line left it a few characters). The level groups
moved to lib/log.ts for both.

The console's own reads are logged at DEBUG on success, like the
healthcheck: at INFO its live tail filled the log with itself.

backend/tests/test_admin_logs.py

@@ -152,3 +152,23 @@ def test_facets_count_the_window_and_name_the_rows_without_a_value(db, admin):
     ]
     assert body["users"] == [{"value": "1", "count": 2}, {"value": "none", "count": 1}]
     assert body["accounts"] == {"1": "admin@example.com"}
+
+
+def test_a_facet_counts_under_every_other_filter_but_not_its_own(db, admin):
+    _add(
+        db,
+        _row(request_id="req-aaaaaaaa"),
+        _row(request_id="req-aaaaaaaa", level="ERROR", sev=17, source="worker"),
+        _row(request_id="req-bbbbbbbb", level="ERROR", sev=17),
+        _row(request_id="req-bbbbbbbb"),
+    )
+
+    body = admin.get(
+        "/api/admin/logs/facets", params={"request_id": "req-aaaaaaaa", "levels": ["ERROR"]}
+    ).json()
+
+    # The pivot narrows every count; the picked level does not zero its sibling (the way back).
+    assert body["levels"] == [{"value": "ERROR", "count": 1}, {"value": "INFO", "count": 1}]
+    assert body["total"] == 2
+    # Every other facet counts under the level filter too.
+    assert body["sources"] == [{"value": "worker", "count": 1}]