fix(logs): the browser's copy of a polled read is quiet too

The server now logs polled reads at DEBUG, and the browser's copy of each
request line promises the server's level: at INFO the unread-count polls
filled My log within minutes and, at Detailed, the shipped log. The server
marks a line it logged at DEBUG with X-Log-Quiet, so the polled-route list
stays in one place.

backend/app/logs.py

@@ -738,6 +738,10 @@ async def log_requests(request, call_next):
         extra={**event("http.request", **attrs), **_request_owner(request, level)},
     )
     response.headers["X-Request-Id"] = rid
+    # The browser logs its own copy of this line (frontend lib/http.ts) and must pick the same level:
+    # it learns "this one is quiet" here instead of keeping a second copy of the polled-route list.
+    if level == logging.DEBUG:
+        response.headers["X-Log-Quiet"] = "1"
     # The template, so the browser's copy of this line groups the same way (frontend lib/http.ts).
     # Only a MATCHED route's: a template never carries a path parameter's value (a share token stays
     # `{token}`), while the raw-path fallback of an unmatched request could — the browser then

backend/tests/test_logs.py

@@ -337,10 +337,13 @@ def test_a_polled_read_is_debug_a_write_to_the_same_route_is_not(sink):
     http = logging.getLogger("siftlode.http")
     http.setLevel(logs.TRACE)
     client = _client()
-    client.get("/api/messages/unread_count")
+    r = client.get("/api/messages/unread_count")
     assert sink.objects()[-1]["level"] == "DEBUG"
-    client.post("/api/messages/unread_count")
+    # ...and says so, for the browser's copy of the line (frontend lib/http.ts).
+    assert r.headers["X-Log-Quiet"] == "1"
+    r = client.post("/api/messages/unread_count")
     assert sink.objects()[-1]["level"] == "INFO"
+    assert "X-Log-Quiet" not in r.headers
     client.get("/api/videos/abc")
     assert sink.objects()[-1]["level"] == "INFO"