fix(suggestion): load full 50-symbol price snapshot + exclude falling-price names from profit buckets

- load_price_snapshot picked the last snapshot by filename (lexicographic),
  selecting a stale 9-symbol collection over the full 50-symbol universe. Now
  picks the snapshot with the latest source.retrieved_at.
- allocate_capital profit buckets now also require momentum > 0 (a falling-price
  name is not 'ทำกำไร'), while momentum/theme_signal stay Optional so the PIT
  backtest path (which doesn't provide them) still allocates.
- Suggestion now allocates across all 50 SET50 names (B1: BGRIM,TTB; B2: BANPU;
  B3: ADVANC,SCB,LH).
- Regression tests for both. Full suite 374 green.

backend/app/simulation.py

@@ -42,8 +42,9 @@ class Candidate:
     dividend_yield: float
     # Owner's "ทำกำไร" definition: a price-trend (momentum) score; and theme
     # signal gate (when provided: must be > 0 to be eligible for profit buckets).
-    # theme_signal=None means "unspecified" (e.g. backtest path) -> not gated.
-    momentum: float = 0.0
+    # None = "unspecified" (e.g. backtest path) -> not gated. momentum=None means
+    # no price-trend signal given -> not gated (rank as 0).
+    momentum: Optional[float] = None
     theme_signal: Optional[float] = None
 
 
@@ -80,13 +81,30 @@ class AllocationResult:
 # B1: price-series loader
 # ---------------------------------------------------------------------------
 def load_price_snapshot(snapshot_path: Optional[Path] = None) -> dict:
-    """Load the newest Yahoo price snapshot: {symbol: {bars: [...]}}."""
+    """Load the newest Yahoo price snapshot: {symbol: {bars: [...]}}.
+
+    'Newest' = the snapshot with the latest ``retrieved_at``, NOT the last
+    filename lexicographically (a partial 9-symbol collection can sort after a
+    full 50-symbol one, which would silently drop most of the universe).
+    """
     if snapshot_path is None:
         snap_dir = _PRICES_DIR / "snapshots"
-        files = sorted(snap_dir.glob("prices-yahoo-chart-*.json"))
+        files = list(snap_dir.glob("prices-yahoo-chart-*.json"))
         if not files:
             raise SimulationError("no Yahoo price snapshot found on disk")
-        snapshot_path = files[-1]
+        # pick the snapshot retrieved most recently by timestamp embedded in
+        # its source metadata (fall back to the newest filename on any error).
+        best: Optional[Path] = None
+        best_ts: Optional[str] = None
+        for f in files:
+            try:
+                blob = json.loads(f.read_text(encoding="utf-8"))
+                ts = (blob.get("source") or {}).get("retrieved_at") or ""
+            except Exception:
+                ts = ""
+            if best is None or (ts and ts > best_ts):
+                best, best_ts = f, ts
+        snapshot_path = best or files[-1]
     data = json.loads(snapshot_path.read_text(encoding="utf-8"))
     return data.get("series", {})
 
@@ -117,15 +135,14 @@ def allocate_capital(
     if not candidates:
         raise SimulationError("no candidates to allocate")
 
-    # "ทำกำไร" = a positive price trend (momentum) across candidates with a
-    # positive theme signal. This is the owner's definition of a price that is
-    # likely to rise in the next 3-6 months — NOT EPS growth / combined score.
-    # Buckets 1 & 2 rank by momentum, gated on theme_signal > 0 (when provided;
-    # theme_signal=None means unspecified and is not gated, e.g. backtest path);
-    # bucket 3 ranks purely by dividend yield (ignoring both score and momentum).
+    # "ทำกำไร" = a price likely to rise in the next 3-6 months, measured by a
+    # POSITIVE price-trend momentum AND a positive theme signal. This is the
+    # owner's definition — NOT EPS growth / combined score. Buckets 1 & 2 rank by
+    # momentum among that pool; bucket 3 ranks purely by dividend yield.
     profit_pool = [c for c in candidates
-                   if c.theme_signal is None or c.theme_signal > 0.0]
-    by_momentum = sorted(profit_pool, key=lambda c: -c.momentum)
+                   if (c.theme_signal is None or c.theme_signal > 0.0)
+                   and (c.momentum is None or c.momentum > 0.0)]
+    by_momentum = sorted(profit_pool, key=lambda c: -(c.momentum or 0.0))
     by_yield = sorted(
         (c for c in candidates if c.is_dividend and c.dividend_yield > 0),
         key=lambda c: -c.dividend_yield,
@@ -152,7 +169,7 @@ def allocate_capital(
         if sort_by == "dividend_yield":
             key = lambda c: -c.dividend_yield
         else:
-            key = lambda c: -c.momentum
+            key = lambda c: -(c.momentum or 0.0)
         for cand in sorted(eligible, key=key):
             if cand.symbol in used:
                 continue