Add spin session functionality and update game mechanics

- Introduced a new `spin_sessions` table to track user spin activities.
- Updated the API to include a new endpoint for spinning games, allowing users to place bets and specify spin counts.
- Enhanced game information structure and added validation for bets and spin counts.
- Implemented the `Forest Fortune` slot game mechanics, including payline evaluation and scatter functionality.
- Updated dependencies in `pyproject.toml` for development and added `httpx` for HTTP requests.
- Added unit tests for the new slot mechanics and API endpoints to ensure functionality and reliability.

app/slots/types.py

@@ -0,0 +1,96 @@
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+from decimal import Decimal
+from typing import Any
+
+
+# grid[reel][row], reel 0..4, row 0..4 (0 = top)
+Grid = list[list[str]]
+
+
+@dataclass
+class PaylineWin:
+    line_index: int
+    symbol: str
+    count: int
+    amount: Decimal
+    path: list[int]
+
+
+@dataclass
+class SpinOutcome:
+    grid: Grid
+    line_wins: list[PaylineWin]
+    scatter_count: int
+    scatter_win: Decimal
+    total_win: Decimal
+    meta_triggered: bool
+
+
+@dataclass
+class SessionMetaState:
+    level: int = 1
+    multiplier: int = 1
+    triggered: bool = False
+
+    def after_trigger(self) -> SessionMetaState:
+        level = self.level + 1
+        return SessionMetaState(level=level, multiplier=level, triggered=True)
+
+
+@dataclass
+class SpinResult:
+    index: int
+    grid: Grid
+    line_wins: list[PaylineWin]
+    scatter_count: int
+    scatter_win: Decimal
+    total_win: Decimal
+    level: int
+    multiplier: int
+    meta_triggered: bool
+
+
+@dataclass
+class SessionResult:
+    bet: Decimal
+    spin_count: int
+    total_bet: Decimal
+    total_win: Decimal
+    max_level: int
+    trigger_count: int
+    spins: list[SpinResult] = field(default_factory=list)
+
+    def to_payload(self) -> dict[str, Any]:
+        return {
+            "bet": str(self.bet),
+            "spin_count": self.spin_count,
+            "total_bet": str(self.total_bet),
+            "total_win": str(self.total_win),
+            "max_level": self.max_level,
+            "trigger_count": self.trigger_count,
+            "spins": [
+                {
+                    "index": s.index,
+                    "grid": s.grid,
+                    "line_wins": [
+                        {
+                            "line_index": w.line_index,
+                            "symbol": w.symbol,
+                            "count": w.count,
+                            "amount": str(w.amount),
+                            "path": w.path,
+                        }
+                        for w in s.line_wins
+                    ],
+                    "scatter_count": s.scatter_count,
+                    "scatter_win": str(s.scatter_win),
+                    "total_win": str(s.total_win),
+                    "level": s.level,
+                    "multiplier": s.multiplier,
+                    "meta_triggered": s.meta_triggered,
+                }
+                for s in self.spins
+            ],
+        }