feat: implement dual-pipeline signal engine service

New service at services/signal_engine/ implementing concurrent heuristic
(deterministic scoring) and probabilistic (Bayesian inference) pipelines
that evaluate technical signals across 6 timeframes (M30-M) and produce
independent BUY/WATCH/SKIP verdicts per ticker per evaluation tick.

Components:
- Input Normalizer: multi-source data assembly with sentinel fallbacks
- Signal Library: Fibonacci, MA Stack, RSI, Cup & Handle, Elliott Wave
- Multi-Timeframe Confluence Engine: weighted scoring with D/W/M anchors
- Hard Filter Engine: macro_bias, valuation, earnings proximity gating
- Heuristic Pipeline: S_total scoring with confidence-gated verdicts
- Probabilistic Pipeline: Bayesian log-odds with regime priors, entropy
  gating, EV_R calculation, and signal correlation penalty
- Exit Engine: stop-loss, targets, trailing ATR-based stops
- Delta Analyzer: pipeline agreement tracking with rolling Redis metrics
- Output Formatter: SignalOutput contract + Recommendation schema mapping
- Worker orchestrator: concurrent pipelines with failure isolation
- Main entry point: queue polling with fail-safe config loading

Infrastructure:
- Migration 039: signal_engine_outputs table with 3 indexes
- Helm chart: signalEngine service entry (processing tier)
- Redis key: QUEUE_SIGNAL_ENGINE constant

Tests: 390 tests (unit + property-based) covering all components
Config: dual_pipeline_enabled=false by default (safe rollout)

tests/test_pbt_signal_engine_models.py

@@ -0,0 +1,144 @@
+# Feature: dual-pipeline-signal-engine, Property: SignalOutput round-trip serialization
+"""Property-based tests for SignalOutput round-trip serialization.
+
+Feature: dual-pipeline-signal-engine
+
+Tests the SignalOutput round-trip serialization property from the design
+specification: for any valid SignalOutput instance, serializing to JSON via
+model_dump_json() and deserializing back via model_validate_json() SHALL
+produce a SignalOutput object equivalent to the original.
+"""
+from __future__ import annotations
+
+from datetime import datetime, timezone
+
+from hypothesis import given, settings
+from hypothesis import strategies as st
+
+from services.signal_engine.models import (
+    ExitSignal,
+    ExitType,
+    SignalOutput,
+    TradePlan,
+)
+
+# ---------------------------------------------------------------------------
+# Property: SignalOutput Round-Trip Serialization
+# Validates: Requirements 10.5, 17.6
+# ---------------------------------------------------------------------------
+
+# ---------------------------------------------------------------------------
+# Hypothesis strategies
+# ---------------------------------------------------------------------------
+
+_finite_float = st.floats(allow_nan=False, allow_infinity=False)
+_non_negative_finite_float = st.floats(
+    min_value=0.0, allow_nan=False, allow_infinity=False,
+)
+_unit_float = st.floats(
+    min_value=0.0, max_value=1.0, allow_nan=False, allow_infinity=False,
+)
+
+_aware_datetime_strategy = st.datetimes(
+    min_value=datetime(2020, 1, 1),
+    max_value=datetime(2030, 12, 31),
+    timezones=st.just(timezone.utc),
+)
+
+_ticker_strategy = st.text(
+    alphabet=st.characters(whitelist_categories=("Lu",)),
+    min_size=1,
+    max_size=5,
+)
+
+_verdict_strategy = st.sampled_from(["BUY", "WATCH", "SKIP"])
+
+_pipeline_mode_strategy = st.sampled_from(["dual_pipeline", "heuristic_only", "probabilistic_only"])
+
+# --- TradePlan strategy ---
+
+_trade_plan_strategy = st.builds(
+    TradePlan,
+    entry_price=_finite_float,
+    stop_loss=_finite_float,
+    target_1=_finite_float,
+    target_2=_finite_float,
+    position_size_pct=_unit_float,
+    max_loss_pct=_unit_float,
+    dual_confirmed=st.booleans(),
+    probabilistic_only=st.booleans(),
+)
+
+# --- ExitSignal strategy ---
+
+_exit_signal_strategy = st.builds(
+    ExitSignal,
+    position_id=st.uuids().map(str),
+    ticker=_ticker_strategy,
+    exit_type=st.sampled_from(list(ExitType)),
+    reason=st.sampled_from(["stop_hit", "target_1_hit", "target_2_hit", "trailing_stop_hit"]),
+    price=_finite_float,
+)
+
+# --- Simple dict strategies for detail payloads ---
+
+_simple_detail_strategy = st.fixed_dictionaries(
+    {},
+    optional={
+        "score": _finite_float,
+        "label": st.text(max_size=20),
+        "count": st.integers(min_value=0, max_value=1000),
+    },
+)
+
+# --- SignalOutput strategy ---
+
+_signal_output_strategy = st.builds(
+    SignalOutput,
+    output_id=st.uuids().map(str),
+    ticker=_ticker_strategy,
+    timestamp=_aware_datetime_strategy,
+    price=_finite_float,
+    heuristic_verdict=_verdict_strategy,
+    heuristic_confidence=_unit_float,
+    heuristic_s_total=_finite_float,
+    probabilistic_verdict=_verdict_strategy,
+    probabilistic_p_up=_unit_float,
+    probabilistic_entropy=_unit_float,
+    probabilistic_ev_r=_finite_float,
+    delta_agreement=st.booleans(),
+    delta_confidence_delta=_non_negative_finite_float,
+    delta_reasons=st.lists(st.text(min_size=1, max_size=50), min_size=0, max_size=5),
+    trade_plan=st.one_of(st.none(), _trade_plan_strategy),
+    exit_signals=st.lists(_exit_signal_strategy, min_size=0, max_size=3),
+    heuristic_detail=_simple_detail_strategy,
+    probabilistic_detail=_simple_detail_strategy,
+    pipeline_mode=_pipeline_mode_strategy,
+    shadow_mode=st.booleans(),
+)
+
+
+# ---------------------------------------------------------------------------
+# Property test
+# ---------------------------------------------------------------------------
+
+
+@given(output=_signal_output_strategy)
+@settings(max_examples=100)
+def test_signal_output_round_trip_serialization(output: SignalOutput) -> None:
+    """**Validates: Requirements 10.5, 17.6**
+
+    For any valid SignalOutput instance, serializing to JSON and then
+    deserializing back SHALL produce a SignalOutput object equivalent
+    to the original.
+    """
+    json_str = output.model_dump_json()
+    restored = SignalOutput.model_validate_json(json_str)
+    assert restored == output, (
+        f"Round-trip failed: deserialized SignalOutput differs from original.\n"
+        f"  ticker: {output.ticker}\n"
+        f"  heuristic_verdict: {output.heuristic_verdict}\n"
+        f"  probabilistic_verdict: {output.probabilistic_verdict}\n"
+        f"  trade_plan present: {output.trade_plan is not None}\n"
+        f"  exit_signals count: {len(output.exit_signals)}"
+    )