fix: deduplicate recommendations and widen position sizing range

- Add dedup check in recommendation worker: skip generation when latest
  rec for same ticker+window has identical action/mode/confidence
- Widen position sizing range (1-10% portfolio, 0.3-2% max loss) and
  factor in trend strength + evidence count for differentiated sizing
- API returns only latest recommendation per ticker by default (DISTINCT ON)
  to eliminate duplicate rows in the frontend list view

services/api/app.py

@@ -450,8 +450,14 @@ async def list_recommendations(
     since: Optional[str] = None,
     limit: int = Query(default=50, le=200),
     offset: int = 0,
+    latest: bool = Query(default=True, description="Return only the latest recommendation per ticker"),
 ):
-    """List recommendations with optional filters."""
+    """List recommendations with optional filters.
+
+    By default (latest=true), returns only the most recent recommendation
+    per ticker to avoid showing duplicate/stale entries. Set latest=false
+    to see the full history.
+    """
     conditions: list[str] = []
     params: list[Any] = []
     idx = 1
@@ -475,17 +481,35 @@ async def list_recommendations(
 
     where = ("WHERE " + " AND ".join(conditions)) if conditions else ""
 
-    rows = await pool.fetch(
-        f"""SELECT r.id, r.ticker, r.action, r.mode, r.confidence,
-                   r.time_horizon, r.thesis, r.invalidation_conditions,
-                   r.portfolio_pct, r.max_loss_pct, r.model_version,
-                   r.risk_classification, r.generated_at
-            FROM recommendations r
-            {where}
-            ORDER BY r.generated_at DESC
-            LIMIT ${idx} OFFSET ${idx + 1}""",
-        *params, limit, offset,
-    )
+    if latest:
+        # Use DISTINCT ON to get only the latest recommendation per ticker
+        rows = await pool.fetch(
+            f"""SELECT DISTINCT ON (r.ticker)
+                       r.id, r.ticker, r.action, r.mode, r.confidence,
+                       r.time_horizon, r.thesis, r.invalidation_conditions,
+                       r.portfolio_pct, r.max_loss_pct, r.model_version,
+                       r.risk_classification, r.generated_at
+                FROM recommendations r
+                {where}
+                ORDER BY r.ticker, r.generated_at DESC""",
+            *params,
+        )
+        # Apply limit/offset manually after DISTINCT ON
+        # Sort by generated_at DESC for the final result
+        rows = sorted(rows, key=lambda r: r["generated_at"], reverse=True)
+        rows = rows[offset:offset + limit]
+    else:
+        rows = await pool.fetch(
+            f"""SELECT r.id, r.ticker, r.action, r.mode, r.confidence,
+                       r.time_horizon, r.thesis, r.invalidation_conditions,
+                       r.portfolio_pct, r.max_loss_pct, r.model_version,
+                       r.risk_classification, r.generated_at
+                FROM recommendations r
+                {where}
+                ORDER BY r.generated_at DESC
+                LIMIT ${idx} OFFSET ${idx + 1}""",
+            *params, limit, offset,
+        )
     results = []
     for r in rows:
         d = _row_to_dict(r)