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_logs.py

@@ -14,7 +14,7 @@ import logging
 from pathlib import Path
 
 import pytest
-from fastapi import FastAPI, Request
+from fastapi import FastAPI, HTTPException, Request
 from fastapi.testclient import TestClient
 
 from app import logs
@@ -213,6 +213,12 @@ def _client() -> TestClient:
     def _health():
         return {"ok": True}
 
+    @app.get("/api/admin/logs/facets")
+    def _log_console(fail: bool = False):
+        if fail:
+            raise HTTPException(status_code=400, detail={"code": "bad_cursor"})
+        return {"ok": True}
+
     @app.get("/boom")
     def _boom():
         raise RuntimeError("kaboom")
@@ -307,6 +313,16 @@ def test_the_healthcheck_is_logged_at_debug_so_it_cannot_drown_the_log(sink):
     assert len(sink.lines) == before
 
 
+def test_the_log_consoles_own_reads_are_debug_but_its_failures_are_not(sink):
+    http = logging.getLogger("siftlode.http")
+    http.setLevel(logs.TRACE)
+    client = _client()
+    client.get("/api/admin/logs/facets")
+    assert sink.objects()[-1]["level"] == "DEBUG"
+    client.get("/api/admin/logs/facets?fail=1")
+    assert sink.objects()[-1]["level"] == "WARNING"
+
+
 def test_a_failing_request_is_logged_by_status_and_an_unhandled_error_is_logged_at_all(sink):
     client = _client()
     client.get("/api/videos/missing/deeper")  # 404 from the router