Remove Oanda auto-execution daemon/executor (not auto-trading)

Deletes oanda_daemon.py, oanda_executor.py, their 28 tests and the daemon-only
config keys (oanda.lot_size/quality_gate/max_hold_bars). The Oanda data
provider and credentials stay — it is the live candle feed. 402 tests.

Claude-Session: https://claude.ai/code/session_01FC4s6VCURFte4dub4xKxYL

config.json.example

@@ -28,10 +28,7 @@
   "oanda": {
     "account_id": "REPLACE_WITH_ACCOUNT_ID",
     "api_token": "REPLACE_WITH_API_TOKEN",
-    "base_url": "https://api-fxpractice.oanda.com",
-    "lot_size": 1,
-    "quality_gate": "C",
-    "max_hold_bars": 300
+    "base_url": "https://api-fxpractice.oanda.com"
   },
   "deepseek": {
     "api_key": "REPLACE_WITH_YOUR_DEEPSEEK_API_KEY_OR_EMPTY",