feat(db): dedup-safe inserts, filter_new_accessions, mark_accession_seen, as-of-date queries

- insert_filing: catch IntegrityError on duplicate accession instead of crashing
- filter_new_accessions: bulk pre-filter entire quarter against DB in chunked IN queries
  (avoids 30min per-row accession_exists loop during resume)
- mark_accession_seen: store placeholder row for derivative-only/empty filings so they
  aren't re-fetched on every resume
- get_recent_buys_for_ticker: accept as_of_date to clamp queries for historical signal gen
- get_all_buys_for_reprocess: return all buy filings ordered by transaction_date for backfill

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

db/db.py

@@ -2,6 +2,7 @@ from datetime import datetime
 from typing import Optional
 
 from sqlalchemy import create_engine, func, select, text, update
+from sqlalchemy.exc import IntegrityError
 from sqlalchemy.orm import Session
 
 import config
@@ -59,8 +60,12 @@ def insert_filing(filing: dict) -> bool:
             post_tx_shares=filing.get("post_tx_shares"),
         )
         session.add(row)
+        try:
             session.commit()
             return True
+        except IntegrityError:
+            session.rollback()
+            return False
 
 
 def accession_exists(accession_number: str) -> bool:
@@ -70,6 +75,40 @@ def accession_exists(accession_number: str) -> bool:
         ) is not None
 
 
+def mark_accession_seen(accession_number: str) -> None:
+    """Store a placeholder row so derivative-only/empty filings aren't re-fetched."""
+    with _session() as session:
+        exists = session.scalar(
+            select(Filing.id).where(Filing.accession_number == accession_number)
+        )
+        if exists is not None:
+            return
+        session.add(Filing(accession_number=accession_number))
+        try:
+            session.commit()
+        except IntegrityError:
+            session.rollback()
+
+
+def filter_new_accessions(accessions: list[str]) -> set[str]:
+    """Return the subset of accessions not already in the DB."""
+    if not accessions:
+        return set()
+    existing: set[str] = set()
+    chunk_size = 900  # SQLite SQLITE_MAX_VARIABLE_NUMBER limit
+    with _session() as session:
+        for i in range(0, len(accessions), chunk_size):
+            chunk = accessions[i:i + chunk_size]
+            existing.update(
+                session.execute(
+                    select(Filing.accession_number).where(
+                        Filing.accession_number.in_(chunk)
+                    )
+                ).scalars().all()
+            )
+    return set(accessions) - existing
+
+
 def get_latest_filed_date() -> Optional[str]:
     with _session() as session:
         return session.scalar(select(func.max(Filing.filed_date)))
@@ -135,10 +174,14 @@ def get_executed_unclosed_signals() -> list[dict]:
         return [_signal_to_dict(r) for r in rows]
 
 
-def get_recent_buys_for_ticker(ticker: str, window_days: int) -> list[dict]:
+def get_recent_buys_for_ticker(
+    ticker: str, window_days: int, as_of_date: Optional[str] = None
+) -> list[dict]:
     from datetime import timedelta
 
-    cutoff = (datetime.utcnow() - timedelta(days=window_days)).strftime("%Y-%m-%d")
+    ref = datetime.strptime(as_of_date, "%Y-%m-%d") if as_of_date else datetime.utcnow()
+    cutoff = (ref - timedelta(days=window_days)).strftime("%Y-%m-%d")
+    ref_str = ref.strftime("%Y-%m-%d")
     with _session() as session:
         rows = session.scalars(
             select(Filing)
@@ -147,12 +190,24 @@ def get_recent_buys_for_ticker(ticker: str, window_days: int) -> list[dict]:
                 Filing.flag == "A",
                 Filing.is_10b51 == False,
                 Filing.transaction_date >= cutoff,
+                Filing.transaction_date <= ref_str,
             )
             .order_by(Filing.transaction_date.desc())
         ).all()
         return [_filing_to_dict(r) for r in rows]
 
 
+def get_all_buys_for_reprocess() -> list[dict]:
+    """Return all buy filings for signal reprocessing (used after bulk ingest)."""
+    with _session() as session:
+        rows = session.scalars(
+            select(Filing)
+            .where(Filing.flag == "A")
+            .order_by(Filing.transaction_date)
+        ).all()
+        return [_filing_to_dict(r) for r in rows]
+
+
 def get_signals_for_backtest(min_score: float, min_cluster_size: int) -> list[dict]:
     with _session() as session:
         rows = session.scalars(