refactor(smart_executor): split monolithic executor into clean service modules

- Extract 7 focused services from smart_executor.py:
  - trade_common: constants, timezone, logging, dry-run state
  - file_utils: file locking + atomic JSON helpers
  - smart_executor_parser: argparse + legacy argument compatibility
  - execution_state: decision deduplication (executions.json)
  - portfolio_service: positions.json + exchange reconciliation
  - exchange_service: ccxt wrapper, balances, order prep
  - trade_execution: buy/sell/rebalance/hold actions
- Turn smart_executor.py into a thin backward-compatible facade
- Fix critical dry-run bug: module-level DRY_RUN copy caused real orders
  in dry-run mode; replace with mutable dict + is_dry_run() function
- Fix dry-run polluting positions.json: skip save_positions() when dry-run
- Fix rebalance dry-run budget: use sell_order cost instead of real balance
- Add full legacy CLI compatibility for old --decision HOLD --dry-run style

src/coinhunter/services/portfolio_service.py

@@ -0,0 +1,57 @@
+"""Portfolio state helpers (positions.json, reconcile with exchange)."""
+from ..runtime import get_runtime_paths
+from .file_utils import load_json_locked, save_json_locked
+from .trade_common import bj_now_iso
+
+PATHS = get_runtime_paths()
+POSITIONS_FILE = PATHS.positions_file
+POSITIONS_LOCK = PATHS.positions_lock
+
+
+def load_positions() -> list:
+    return load_json_locked(POSITIONS_FILE, POSITIONS_LOCK, {"positions": []}).get("positions", [])
+
+
+def save_positions(positions: list):
+    save_json_locked(POSITIONS_FILE, POSITIONS_LOCK, {"positions": positions})
+
+
+def upsert_position(positions: list, position: dict):
+    sym = position["symbol"]
+    for i, existing in enumerate(positions):
+        if existing.get("symbol") == sym:
+            positions[i] = position
+            return positions
+    positions.append(position)
+    return positions
+
+
+def reconcile_positions_with_exchange(ex, positions: list):
+    from .exchange_service import fetch_balances
+
+    balances = fetch_balances(ex)
+    existing_by_symbol = {p.get("symbol"): p for p in positions}
+    reconciled = []
+    for asset, qty in balances.items():
+        if asset == "USDT":
+            continue
+        if qty <= 0:
+            continue
+        sym = f"{asset}USDT"
+        old = existing_by_symbol.get(sym, {})
+        reconciled.append(
+            {
+                "account_id": old.get("account_id", "binance-main"),
+                "symbol": sym,
+                "base_asset": asset,
+                "quote_asset": "USDT",
+                "market_type": "spot",
+                "quantity": qty,
+                "avg_cost": old.get("avg_cost"),
+                "opened_at": old.get("opened_at", bj_now_iso()),
+                "updated_at": bj_now_iso(),
+                "note": old.get("note", "Reconciled from Binance balances"),
+            }
+        )
+    save_positions(reconciled)
+    return reconciled, balances