feat(agent): in-UI log console + a real styling pass on the control page

- logbuf.py: bounded in-memory log ring buffer + a logging.Handler on the root
  logger; GET /logs serves it; the control page polls it into a console pane —
  so runs are monitorable without `docker logs`. worker now logs autoscale moves
  (one line per change, with jobs/s + util + VRAM) and job failures (job + image
  + reason); detectors already log load/disable.
- Restyled the whole control page: a proper dark layout with a header + live
  connection pill, cards (Control / Status / Logs), a styled Auto switch +
  worker stepper, status tiles, separate GPU-util and VRAM meters, and the log
  console. No longer feels like an afterthought; all the existing control hooks
  are preserved.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ttrj5P7upUTueSfoJcxEqa

agent/fc_agent/logbuf.py

@@ -0,0 +1,40 @@
+"""In-memory log ring buffer so the control UI can show recent agent logs
+(detector loads, job errors, autoscaler decisions, outage back-offs) without
+needing `docker logs`. A bounded deque holds the last N formatted lines; a
+logging.Handler appends to it; the UI polls /logs."""
+import logging
+from collections import deque
+
+LINES: deque[str] = deque(maxlen=600)
+
+
+class RingHandler(logging.Handler):
+    def emit(self, record: logging.LogRecord) -> None:
+        try:
+            LINES.append(self.format(record))
+        except Exception:
+            pass
+
+
+_installed = False
+
+
+def install(level: int = logging.INFO) -> None:
+    """Attach the ring handler to the root logger once. fc_agent module loggers
+    propagate to root, so their records land here."""
+    global _installed
+    if _installed:
+        return
+    _installed = True
+    h = RingHandler()
+    h.setFormatter(
+        logging.Formatter("%(asctime)s %(levelname)s %(name)s: %(message)s", "%H:%M:%S")
+    )
+    root = logging.getLogger()
+    root.addHandler(h)
+    if root.level == logging.NOTSET or root.level > level:
+        root.setLevel(level)
+    # Keep the buffer signal-rich: drop the per-request access spam + ultralytics
+    # banner noise to WARNING.
+    logging.getLogger("uvicorn.access").setLevel(logging.WARNING)
+    logging.getLogger("ultralytics").setLevel(logging.WARNING)