news: auto-tag headlines + market-aware cadence + filter UI

- Move news_job from hourly to 3x/hour (cron 10,30,50), with a CadencePolicy
  gate that throttles to active hours (07-21 UTC weekdays at 20 min), off-hours
  (3 h), weekends (6 h). Keeps the daytime feed fresh without spamming RSS
  sources overnight.
- Tag each headline on ingestion via DeepSeek (BATCH_SIZE=25, max_tokens=4000,
  json.JSONDecoder().raw_decode + per-row regex recovery for resilient parsing).
  Vocabulary: 16 tags including new EU / USA / AI / Conflict. NULL tags are
  picked up automatically on the next news_job run, so back-tagging is implicit
  rather than a separate migration step.
- Tag UI: pill bar above the feed with off → include → exclude cycle on click;
  shift-click jumps straight to exclude. State persists in localStorage and is
  injected into /api/news requests via htmx:configRequest. Per-row chips sit to
  the right of the headline (new 5-column grid: age | source | title | tags |
  UTC) so vertical density stays high.
- Strategic log header bug: model was hallucinating "(Updated 21:30 UTC)" in
  future tense. Bumped PROMPT_VERSION 6→7, added explicit ban on time-of-day
  clauses, and supply the actual current UTC time in the user prompt so the
  model has no need to invent one.

Migration 0012 adds headlines.tags (JSON, nullable). Tests cover vocabulary
integrity, validation/normalisation, and the JSON-recovery parser (17 tests).

app/services/cadence.py

@@ -29,6 +29,11 @@ class CadencePolicy:
         (7, 21),    # EU/US (LSE open through NYSE close)
         # (0, 8),   # Asia (Tokyo + HK/Shanghai) — uncomment to add
     )
+    # Minimum gap between successful runs DURING the active window. The
+    # cron may fire more frequently than this — we just skip until enough
+    # time has passed since the last success. Default 0 means "run on
+    # every cron fire" (the original AI-job behaviour).
+    active_gap_h: float = 0.0
     # Minimum gap between successful runs outside the active window.
     off_hours_gap_h: float = 4.0
     weekend_gap_h: float = 12.0
@@ -44,7 +49,7 @@ class CadencePolicy:
         if now.weekday() >= 5:
             return self.weekend_gap_h
         if self.is_active_window(now):
-            return 0.0  # always run during the active window
+            return self.active_gap_h
         return self.off_hours_gap_h
 
     def should_run(
@@ -55,8 +60,6 @@ class CadencePolicy:
         """Returns (should_run, reason). The reason is human-readable for logs
         and the job_runs.error column when a run is skipped."""
         now = now or datetime.now(timezone.utc)
-        if self.is_active_window(now):
-            return True, "active window"
         min_gap = self.min_gap_hours(now)
         if last_success_at is None:
             return True, "no prior successful run"
@@ -64,9 +67,27 @@ class CadencePolicy:
         if last_success_at.tzinfo is None:
             last_success_at = last_success_at.replace(tzinfo=timezone.utc)
         age_h = (now - last_success_at).total_seconds() / 3600.0
+        if min_gap <= 0 and self.is_active_window(now):
+            return True, "active window"
         if age_h >= min_gap:
-            return True, f"off-hours but last run {age_h:.1f}h ago (≥ {min_gap}h)"
-        return False, f"off-hours throttled — last run {age_h:.1f}h ago (< {min_gap}h)"
+            band = "active" if self.is_active_window(now) else (
+                "weekend" if now.weekday() >= 5 else "off-hours"
+            )
+            return True, f"{band}: last run {age_h:.2f}h ago (≥ {min_gap:.2f}h)"
+        band = "active" if self.is_active_window(now) else (
+            "weekend" if now.weekday() >= 5 else "off-hours"
+        )
+        return False, f"{band} throttled — last run {age_h:.2f}h ago (< {min_gap:.2f}h)"
 
 
+# AI jobs: run hot during the active window, throttle off-hours.
 DEFAULT_POLICY = CadencePolicy()
+
+# News + tagging: 3 runs/hour during the active window (20-min gap),
+# every 3h off-hours, every 6h on weekends. Cron fires every 20 min;
+# the policy gates whether each fire actually does work.
+NEWS_POLICY = CadencePolicy(
+    active_gap_h=1.0 / 3.0,    # 20 minutes
+    off_hours_gap_h=3.0,
+    weekend_gap_h=6.0,
+)