feat: strategy builder

backend/services/database.py

@@ -11,7 +11,16 @@ DB_PATH = os.path.join(os.path.dirname(__file__), "..", "data", "geooptions.db")
 
 
 def get_conn() -> sqlite3.Connection:
-    conn = sqlite3.connect(DB_PATH)
+    # WAL mode lets readers and a writer proceed concurrently instead of taking the default
+    # rollback-journal's exclusive lock on every write — with several background schedulers
+    # (Saxo snapshots, wavelet refresh, macro gauge...) hitting this same file, that exclusive
+    # lock is what surfaces as "sqlite3.OperationalError: database is locked". busy_timeout is
+    # the second line of defense: a connection that still finds the file locked waits (up to
+    # 30s) instead of raising immediately, covering any writer that briefly holds it even
+    # under WAL (a concurrent writer, not readers).
+    conn = sqlite3.connect(DB_PATH, timeout=30)
+    conn.execute("PRAGMA journal_mode=WAL")
+    conn.execute("PRAGMA busy_timeout=30000")
     conn.row_factory = sqlite3.Row
     return conn