Multi-strategy UI

Adds a "Strategies (multi)" panel: add/remove strategy rows (strategy, symbol,
timeframe, per-strategy params and weight), start all, stop all and kill all,
plus a per-strategy status table (allocation, equity, P&L, halted). Polls
/api/bot/status alongside the existing status. Includes component tests.

frontend/src/api.js

@@ -4,6 +4,8 @@ const http = axios.create({ baseURL: '/api', timeout: 10000 })
 
 export const getVersion = () => http.get('/version').then((r) => r.data)
 export const getStatus = () => http.get('/status').then((r) => r.data)
+export const getMultiStatus = () => http.get('/bot/status').then((r) => r.data)
+export const startMany = (payload) => http.post('/bot/start-many', payload).then((r) => r.data)
 export const getStrategies = () => http.get('/strategies').then((r) => r.data)
 export const getPositions = () => http.get('/positions').then((r) => r.data)
 export const getOrders = () => http.get('/orders').then((r) => r.data)