fix: align production defaults and close review parity gaps

Ship greenfield min_rr=2.0 and conf=0, read-only Structural S/R, indicator
cache invalidation, and UI/gate language that treats GTL as screening not exit.
Align strategy_rank missing-vol fallback live vs backtest, single-source
PRIMARY_TARGET_MIN_RR, expand prod parity tests, and drop dead FE clients.

tests/unit/test_activation_settings.py

@@ -26,7 +26,7 @@ class TestActivationConfig:
         config = await get_activation_config(session)
         assert config == {
             "min_momentum_percentile": 80.0,
-            "min_rr": 1.2,
+            "min_rr": 2.0,
             "min_confidence": 0.0,  # off — the July 2026 ablation showed it adds nothing
             "require_high_conviction": False,
             "exclude_conflicts": False,
@@ -47,7 +47,7 @@ class TestActivationConfig:
     async def test_partial_update_keeps_other_value(self, session: AsyncSession):
         await update_activation_config(session, {"min_confidence": 80.0})
         config = await get_activation_config(session)
-        assert config["min_rr"] == 1.2  # default untouched
+        assert config["min_rr"] == 2.0  # default untouched
         assert config["min_confidence"] == 80.0
 
     async def test_rejects_out_of_range_momentum_percentile(self, session: AsyncSession):