feat: implement fresh wallet detection algorithm (#14)

Add FreshWalletDetector class that identifies trades from fresh wallets
and generates alert signals with confidence scores.

Features:
- FreshWalletSignal dataclass with trade/wallet data and confidence
- Configurable thresholds for nonce, age, and minimum trade size
- Confidence scoring based on wallet freshness and trade characteristics
- Batch analysis support with parallel processing
- Integration with WalletAnalyzer from profiler module

Confidence scoring:
- Base: 0.5 (fresh wallet detected)
- +0.2 if nonce == 0 (brand new)
- +0.1 if age < 2 hours (very young)
- +0.1 if trade size > $10,000 (large trade)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/polymarket_insider_tracker/detector/models.py

@@ -0,0 +1,73 @@
+"""Data models for the detector module."""
+
+from dataclasses import dataclass, field
+from datetime import UTC, datetime
+from decimal import Decimal
+
+from polymarket_insider_tracker.ingestor.models import TradeEvent
+from polymarket_insider_tracker.profiler.models import WalletProfile
+
+
+@dataclass(frozen=True)
+class FreshWalletSignal:
+    """Signal emitted when a fresh wallet makes a suspicious trade.
+
+    This signal combines trade event data with wallet profile analysis
+    to produce a confidence score indicating the likelihood of suspicious
+    activity.
+
+    Attributes:
+        trade_event: The original trade event that triggered this signal.
+        wallet_profile: Analyzed profile of the trader's wallet.
+        confidence: Overall confidence score (0.0 to 1.0).
+        factors: Individual factor scores contributing to confidence.
+        timestamp: When this signal was generated.
+    """
+
+    trade_event: TradeEvent
+    wallet_profile: WalletProfile
+    confidence: float
+    factors: dict[str, float]
+    timestamp: datetime = field(default_factory=lambda: datetime.now(UTC))
+
+    @property
+    def wallet_address(self) -> str:
+        """Return the wallet address from the trade event."""
+        return self.trade_event.wallet_address
+
+    @property
+    def market_id(self) -> str:
+        """Return the market ID from the trade event."""
+        return self.trade_event.market_id
+
+    @property
+    def trade_size_usdc(self) -> Decimal:
+        """Return the trade size in USDC (notional value)."""
+        return self.trade_event.notional_value
+
+    @property
+    def is_high_confidence(self) -> bool:
+        """Return True if confidence exceeds 0.7."""
+        return self.confidence >= 0.7
+
+    @property
+    def is_very_high_confidence(self) -> bool:
+        """Return True if confidence exceeds 0.85."""
+        return self.confidence >= 0.85
+
+    def to_dict(self) -> dict[str, object]:
+        """Serialize to dictionary for Redis stream publishing."""
+        return {
+            "wallet_address": self.wallet_address,
+            "market_id": self.market_id,
+            "trade_id": self.trade_event.trade_id,
+            "trade_size": str(self.trade_size_usdc),
+            "trade_side": self.trade_event.side,
+            "trade_price": str(self.trade_event.price),
+            "wallet_nonce": self.wallet_profile.nonce,
+            "wallet_age_hours": self.wallet_profile.age_hours,
+            "wallet_is_fresh": self.wallet_profile.is_fresh,
+            "confidence": self.confidence,
+            "factors": self.factors,
+            "timestamp": self.timestamp.isoformat(),
+        }