fix: blank company charts + competitor GUIDs instead of tickers

Trend charts blank:
- trend_windows uses upsert (1 row per ticker/window), so charts had
  at most 1 data point. Added trend_history table (migration 024) that
  appends every snapshot. New /api/trends/history endpoint serves the
  time series. Frontend now uses useTrendHistory for charts and
  useTrends for the latest summary card.

Competitor GUIDs:
- list_competitors query returned raw company_b_id UUIDs without
  joining companies table. Added LEFT JOIN with CASE to resolve the
  other company's ticker and legal_name. Updated Pydantic model to
  include enriched fields. Frontend fallback changed from truncated
  UUID to ticker/legal_name/Unknown.

services/aggregation/worker.py

@@ -742,11 +742,23 @@ RETURNING id
 """
 
 
+_INSERT_TREND_HISTORY = """
+INSERT INTO trend_history (
+    entity_type, entity_id, "window", trend_direction,
+    trend_strength, confidence, contradiction_score,
+    dominant_catalysts, material_risks, generated_at
+) VALUES ($1, $2, $3, $4, $5, $6, $7, $8::jsonb, $9::jsonb, $10)
+"""
+
+
 async def persist_trend_summary(
     pool: asyncpg.Pool,
     summary: TrendSummary,
 ) -> str:
-    """Insert a trend summary row and return its UUID."""
+    """Insert a trend summary row and return its UUID.
+
+    Also appends a snapshot to trend_history for time-series charting.
+    """
     row = await pool.fetchrow(
         _UPSERT_TREND,
         summary.entity_type,
@@ -764,7 +776,28 @@ async def persist_trend_summary(
         json.dumps(summary.market_context.model_dump() if summary.market_context else {}, default=str),
         summary.generated_at,
     )
-    return str(row["id"])
+    trend_id = str(row["id"])
+
+    # Append to trend_history for time-series charts
+    try:
+        await pool.execute(
+            _INSERT_TREND_HISTORY,
+            summary.entity_type,
+            summary.entity_id,
+            summary.window.value,
+            summary.trend_direction.value,
+            summary.trend_strength,
+            summary.confidence,
+            summary.contradiction_score,
+            json.dumps(summary.dominant_catalysts),
+            json.dumps(summary.material_risks),
+            summary.generated_at,
+        )
+    except Exception:
+        # Don't fail the main upsert if history insert fails (table may not exist yet)
+        logger.debug("Could not insert trend history for %s/%s", summary.entity_id, summary.window.value, exc_info=True)
+
+    return trend_id
 
 
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