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.

frontend/src/composables/useBacktest.ts

@@ -0,0 +1,150 @@
+/**
+ * Composable for managing backtest state across components.
+ */
+import { ref, computed } from 'vue'
+import type { BacktestResult, BacktestSummary, StrategyInfo, SymbolInfo } from '@/api/types'
+import { getStrategies, getSymbols, getBacktests, getBacktest, runBacktest, deleteBacktest } from '@/api/client'
+import type { BacktestRequest } from '@/api/types'
+
+// Shared state
+const strategies = ref<StrategyInfo[]>([])
+const symbols = ref<SymbolInfo[]>([])
+const runs = ref<BacktestSummary[]>([])
+const currentResult = ref<BacktestResult | null>(null)
+const selectedRuns = ref<string[]>([])
+const loading = ref(false)
+const error = ref<string | null>(null)
+
+// Computed
+const symbolsByMarket = computed(() => {
+  const grouped: Record<string, SymbolInfo[]> = {}
+  for (const s of symbols.value) {
+    const key = `${s.market_type}`
+    if (!grouped[key]) grouped[key] = []
+    grouped[key].push(s)
+  }
+  return grouped
+})
+
+export function useBacktest() {
+  /**
+   * Load strategies and symbols on app init.
+   */
+  async function init() {
+    try {
+      const [stratRes, symRes] = await Promise.all([
+        getStrategies(),
+        getSymbols(),
+      ])
+      strategies.value = stratRes.strategies
+      symbols.value = symRes.symbols
+    } catch (e) {
+      error.value = `Failed to load initial data: ${e}`
+    }
+  }
+
+  /**
+   * Refresh the run history list.
+   */
+  async function refreshRuns() {
+    try {
+      const res = await getBacktests({ limit: 100 })
+      runs.value = res.runs
+    } catch (e) {
+      error.value = `Failed to load runs: ${e}`
+    }
+  }
+
+  /**
+   * Execute a new backtest.
+   */
+  async function executeBacktest(request: BacktestRequest) {
+    loading.value = true
+    error.value = null
+    try {
+      const result = await runBacktest(request)
+      currentResult.value = result
+      await refreshRuns()
+      return result
+    } catch (e: unknown) {
+      const msg = e instanceof Error ? e.message : String(e)
+      error.value = `Backtest failed: ${msg}`
+      throw e
+    } finally {
+      loading.value = false
+    }
+  }
+
+  /**
+   * Load a specific run by ID.
+   */
+  async function loadRun(runId: string) {
+    loading.value = true
+    error.value = null
+    try {
+      const result = await getBacktest(runId)
+      currentResult.value = result
+      return result
+    } catch (e) {
+      error.value = `Failed to load run: ${e}`
+      throw e
+    } finally {
+      loading.value = false
+    }
+  }
+
+  /**
+   * Delete a run.
+   */
+  async function removeRun(runId: string) {
+    try {
+      await deleteBacktest(runId)
+      await refreshRuns()
+      if (currentResult.value?.run_id === runId) {
+        currentResult.value = null
+      }
+      selectedRuns.value = selectedRuns.value.filter(id => id !== runId)
+    } catch (e) {
+      error.value = `Failed to delete run: ${e}`
+    }
+  }
+
+  /**
+   * Toggle run selection for comparison.
+   */
+  function toggleRunSelection(runId: string) {
+    const idx = selectedRuns.value.indexOf(runId)
+    if (idx >= 0) {
+      selectedRuns.value.splice(idx, 1)
+    } else if (selectedRuns.value.length < 5) {
+      selectedRuns.value.push(runId)
+    }
+  }
+
+  /**
+   * Clear all selections.
+   */
+  function clearSelections() {
+    selectedRuns.value = []
+  }
+
+  return {
+    // State
+    strategies,
+    symbols,
+    symbolsByMarket,
+    runs,
+    currentResult,
+    selectedRuns,
+    loading,
+    error,
+    // Actions
+    init,
+    refreshRuns,
+    executeBacktest,
+    loadRun,
+    removeRun,
+    toggleRunSelection,
+    clearSelections,
+  }
+}