feat: upcoming economic releases panel on Calendar page

- eco.py: GET /api/eco/upcoming — estimates next release date per series
  from last stored date + frequency + typical publication lag; returns
  status (imminent/due_soon/upcoming/scheduled/overdue/no_data)
- CalendarPage.tsx: UpcomingPanel component in right sidebar showing
  next expected dates, J-N countdown, last value + direction signal;
  color-coded by urgency (orange=cette semaine, yellow=attendu, blue=ce mois)

Dates are approximate (freq + typical lag), not official FRED schedule.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/routers/eco.py

@@ -192,6 +192,104 @@ def list_eco_events(
     return {"total": total, "offset": offset, "limit": limit, "events": events}
 
 
+# ── Upcoming releases ────────────────────────────────────────────────────────
+
+# Typical publication lag (days) after the end of the reference period
+_RELEASE_LAG: Dict[str, Dict[str, Any]] = {
+    "PAYEMS":          {"freq_days": 30,  "lag_days": 35, "note": "1er vendredi du mois"},
+    "UNRATE":          {"freq_days": 30,  "lag_days": 35, "note": "Avec NFP"},
+    "CPIAUCSL":        {"freq_days": 30,  "lag_days": 15, "note": "Mi-mois"},
+    "CPILFESL":        {"freq_days": 30,  "lag_days": 15, "note": "Avec CPI"},
+    "PCEPILFE":        {"freq_days": 30,  "lag_days": 30, "note": "Fin de mois"},
+    "FEDFUNDS":        {"freq_days": 45,  "lag_days": 45, "note": "Réunion FOMC (~8/an)"},
+    "ICSA":            {"freq_days": 7,   "lag_days": 4,  "note": "Chaque jeudi"},
+    "GDPC1":           {"freq_days": 90,  "lag_days": 30, "note": "Estimation avancée BEA"},
+    "BAMLH0A0HYM2":    {"freq_days": 7,   "lag_days": 1,  "note": "Hebdomadaire"},
+    "T10Y2Y":          {"freq_days": 7,   "lag_days": 1,  "note": "Hebdomadaire"},
+    "T10Y3M":          {"freq_days": 7,   "lag_days": 1,  "note": "Hebdomadaire"},
+}
+
+
+@router.get("/upcoming")
+def upcoming_events() -> List[Dict[str, Any]]:
+    """Estimate next release dates for each series based on last stored date + typical lag."""
+    from services.database import get_conn
+    from services.fred_bootstrap import FRED_SERIES
+    from datetime import date, timedelta
+
+    conn = get_conn()
+    today = date.today()
+    upcoming = []
+
+    for sid, lag_info in _RELEASE_LAG.items():
+        meta = FRED_SERIES.get(sid)
+        if not meta:
+            continue
+        try:
+            row = conn.execute(
+                "SELECT MAX(event_date), actual_value, actual_unit, surprise_direction "
+                "FROM economic_events WHERE series_id=?",
+                (sid,),
+            ).fetchone()
+            if not row or not row[0]:
+                # No data in DB yet — still show as "not loaded"
+                upcoming.append({
+                    "series_id": sid,
+                    "name": meta["name"],
+                    "note": lag_info["note"],
+                    "category": meta["category"],
+                    "last_release": None,
+                    "last_value": None,
+                    "last_unit": meta["unit"],
+                    "last_direction": None,
+                    "next_expected": None,
+                    "days_until": None,
+                    "status": "no_data",
+                })
+                continue
+
+            last_date = date.fromisoformat(row[0])
+            freq_days = lag_info["freq_days"]
+            lag_days  = lag_info["lag_days"]
+
+            # Next expected = last ref period end + lag
+            next_release = last_date + timedelta(days=freq_days + lag_days)
+
+            days_until = (next_release - today).days
+
+            if days_until < -freq_days:
+                # Very overdue — likely bootstrap missing recent data
+                status = "overdue"
+            elif days_until < 0:
+                status = "due_soon"   # probably released, not yet in DB
+            elif days_until <= 7:
+                status = "imminent"
+            elif days_until <= 30:
+                status = "upcoming"
+            else:
+                status = "scheduled"
+
+            upcoming.append({
+                "series_id":    sid,
+                "name":         meta["name"],
+                "note":         lag_info["note"],
+                "category":     meta["category"],
+                "last_release": str(last_date),
+                "last_value":   round(float(row[1]), 3) if row[1] is not None else None,
+                "last_unit":    row[2] or meta["unit"],
+                "last_direction": row[3],
+                "next_expected": str(next_release),
+                "days_until":   days_until,
+                "status":       status,
+            })
+        except Exception as e:
+            logger.debug(f"[eco/upcoming] {sid}: {e}")
+
+    conn.close()
+    upcoming.sort(key=lambda x: (x["next_expected"] or "9999", x["series_id"]))
+    return upcoming
+
+
 # ── DB count summary ──────────────────────────────────────────────────────────
 
 @router.get("/status")