Implement FastAPI backend and Vue 3 frontend for Lowkey Backtest UI

- Added FastAPI backend with core API endpoints for strategies, backtests, and data management.
- Introduced Vue 3 frontend with a dark theme, enabling users to run backtests, adjust parameters, and compare results.
- Implemented Pydantic schemas for request/response validation and SQLAlchemy models for database interactions.
- Enhanced project structure with dedicated modules for services, routers, and components.
- Updated dependencies in `pyproject.toml` and `frontend/package.json` to include FastAPI, SQLAlchemy, and Vue-related packages.
- Improved `.gitignore` to exclude unnecessary files and directories.

api/models/schemas.py

@@ -0,0 +1,162 @@
+"""
+Pydantic schemas for API request/response models.
+"""
+from datetime import datetime
+from typing import Any
+
+from pydantic import BaseModel, Field
+
+
+# --- Strategy Schemas ---
+
+class StrategyParam(BaseModel):
+    """Single strategy parameter definition."""
+    name: str
+    value: Any
+    param_type: str = Field(description="Type: int, float, bool, list")
+    min_value: float | None = None
+    max_value: float | None = None
+    description: str | None = None
+
+
+class StrategyInfo(BaseModel):
+    """Strategy information with parameters."""
+    name: str
+    display_name: str
+    market_type: str
+    default_leverage: int
+    default_params: dict[str, Any]
+    grid_params: dict[str, Any]
+
+
+class StrategiesResponse(BaseModel):
+    """Response for GET /api/strategies."""
+    strategies: list[StrategyInfo]
+
+
+# --- Symbol/Data Schemas ---
+
+class SymbolInfo(BaseModel):
+    """Available symbol information."""
+    symbol: str
+    exchange: str
+    market_type: str
+    timeframes: list[str]
+    start_date: str | None = None
+    end_date: str | None = None
+    row_count: int = 0
+
+
+class DataStatusResponse(BaseModel):
+    """Response for GET /api/data/status."""
+    symbols: list[SymbolInfo]
+
+
+# --- Backtest Schemas ---
+
+class BacktestRequest(BaseModel):
+    """Request body for POST /api/backtest."""
+    strategy: str
+    symbol: str
+    exchange: str = "okx"
+    timeframe: str = "1h"
+    market_type: str = "perpetual"
+    start_date: str | None = None
+    end_date: str | None = None
+    init_cash: float = 10000.0
+    leverage: int | None = None
+    fees: float | None = None
+    slippage: float = 0.001
+    sl_stop: float | None = None
+    tp_stop: float | None = None
+    sl_trail: bool = False
+    params: dict[str, Any] = Field(default_factory=dict)
+
+
+class TradeRecord(BaseModel):
+    """Single trade record."""
+    entry_time: str
+    exit_time: str | None = None
+    entry_price: float
+    exit_price: float | None = None
+    size: float
+    direction: str
+    pnl: float | None = None
+    return_pct: float | None = None
+    status: str = "closed"
+
+
+class EquityPoint(BaseModel):
+    """Single point on equity curve."""
+    timestamp: str
+    value: float
+    drawdown: float = 0.0
+
+
+class BacktestMetrics(BaseModel):
+    """Backtest performance metrics."""
+    total_return: float
+    benchmark_return: float = 0.0
+    alpha: float = 0.0
+    sharpe_ratio: float
+    max_drawdown: float
+    win_rate: float
+    total_trades: int
+    profit_factor: float | None = None
+    avg_trade_return: float | None = None
+    total_fees: float = 0.0
+    total_funding: float = 0.0
+    liquidation_count: int = 0
+    liquidation_loss: float = 0.0
+    adjusted_return: float | None = None
+
+
+class BacktestResult(BaseModel):
+    """Complete backtest result."""
+    run_id: str
+    strategy: str
+    symbol: str
+    market_type: str
+    timeframe: str
+    start_date: str
+    end_date: str
+    leverage: int
+    params: dict[str, Any]
+    metrics: BacktestMetrics
+    equity_curve: list[EquityPoint]
+    trades: list[TradeRecord]
+    created_at: str
+
+
+class BacktestSummary(BaseModel):
+    """Summary for backtest list view."""
+    run_id: str
+    strategy: str
+    symbol: str
+    market_type: str
+    timeframe: str
+    total_return: float
+    sharpe_ratio: float
+    max_drawdown: float
+    total_trades: int
+    created_at: str
+    params: dict[str, Any]
+
+
+class BacktestListResponse(BaseModel):
+    """Response for GET /api/backtests."""
+    runs: list[BacktestSummary]
+    total: int
+
+
+# --- Comparison Schemas ---
+
+class CompareRequest(BaseModel):
+    """Request body for POST /api/compare."""
+    run_ids: list[str] = Field(min_length=2, max_length=5)
+
+
+class CompareResult(BaseModel):
+    """Comparison of multiple backtest runs."""
+    runs: list[BacktestResult]
+    param_diff: dict[str, list[Any]]