fix(unifi): the Overview's history buckets on Postgres; devices name their state (#5207)

#5207 "UniFi Overview tab: func.strftime is SQLite-only": the WAN and
client sparklines bucketed with strftime('%s'), which Postgres lacks, so
/plugins/unifi/rows failed. Traefik's date_bin bucket moves to
core/time_range.time_bucket and both plugins use it. Devices list offline
and failing first, and a state other than online is named (Upgrading,
Adopting, Heartbeat missed...) instead of drawn as Down.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

plugins/traefik/routes.py

@@ -10,7 +10,7 @@ import time
 
 from steward.auth.middleware import require_role
 from steward.models.users import UserRole
-from steward.core.time_range import parse_range, DEFAULT_RANGE, bucket_seconds, subsample
+from steward.core.time_range import parse_range, DEFAULT_RANGE, bucket_seconds, subsample, time_bucket
 from steward.core.formatting import cert_left, status_class
 from steward.models.metrics import PluginMetricLatest
 from .models import TraefikAccessSummary, TraefikCert, TraefikGlobalStat, TraefikMetric
@@ -430,15 +430,6 @@ async def widget_access_log():
                                  summary=summary, widget_id=widget_id)
 
 
-def _time_bucket(column, seconds: int):
-    """The start of the `seconds`-wide window a timestamp falls in, as
-    host_agent/metrics_query.py buckets. Integer epoch / int rendered as
-    numeric division (no two scrapes shared a bucket) and overflowed int4
-    after 2038 (#5256)."""
-    return func.date_bin(func.make_interval(0, 0, 0, 0, 0, 0, int(seconds)), column,
-                         func.to_timestamp(0)).label("bucket")
-
-
 # A rows or widget request past this logs where its time went, phase by
 # phase, so a slow query names itself (#5355: 8 s on every poll, warm).
 SLOW_PAGE_SECONDS = 1.0
@@ -473,7 +464,7 @@ async def router_history(db, names: list[str], since, bucket_secs: int) -> dict[
     history: dict[str, list] = {n: [] for n in names}
     if not history:
         return history
-    bucket_col = _time_bucket(TraefikMetric.scraped_at, bucket_secs)
+    bucket_col = time_bucket(TraefikMetric.scraped_at, bucket_secs)
     result = await db.execute(
         select(
             TraefikMetric.router_name,
@@ -509,7 +500,7 @@ async def request_history(db, since, bucket_seconds: int) -> list[dict]:
         .group_by(TraefikMetric.scraped_at)
         .subquery()
     )
-    bucket_col = _time_bucket(per_scrape.c.at, bucket_seconds)
+    bucket_col = time_bucket(per_scrape.c.at, bucket_seconds)
     rows = (await db.execute(
         select(
             func.avg(per_scrape.c.req).label("req_rate"),