feat: add pagination for trade history in backtest

Backend:
- Added pagination to /trades endpoint with page and per_page params
- Returns paginated trades with metadata (page, total_pages, has_next, has_prev)

Frontend:
- Added pagination controls for trade history (Prev/Next buttons)
- Shows current page info and total trades
- Trades are loaded on-demand when expanded

API changes:
- GET /bots/{id}/backtest/{runId}/trades?page=1&per_page=5
- Response includes: trades, total_trades, page, per_page, total_pages, has_next, has_prev

src/backend/app/api/backtest.py

@@ -181,10 +181,17 @@ def get_backtest(
 def get_backtest_trades(
     bot_id: str,
     run_id: str,
+    page: int = 1,
+    per_page: int = 5,
     current_user: User = Depends(get_current_user),
     db: Session = Depends(get_db),
 ):
-    """Get trade history for a specific backtest."""
+    """Get paginated trade history for a specific backtest.
+    
+    Args:
+        page: Page number (1-indexed)
+        per_page: Number of trades per page (default 5, max 20)
+    """
     bot = db.query(Bot).filter(Bot.id == bot_id).first()
     if not bot:
         raise HTTPException(
@@ -211,12 +218,30 @@ def get_backtest_trades(
     if isinstance(result, str):
         import json
         result = json.loads(result)
-    trades = result.get("trades", []) or []
+    all_trades = result.get("trades", []) or []
+    total_trades = len(all_trades)
+    
+    # Validate pagination params
+    per_page = min(max(per_page, 1), 20)  # Clamp between 1 and 20
+    page = max(page, 1)
+    
+    # Calculate pagination
+    total_pages = max(1, (total_trades + per_page - 1) // per_page) if total_trades > 0 else 1
+    start_idx = (page - 1) * per_page
+    end_idx = start_idx + per_page
+    
+    # Get page of trades (return empty list if start_idx >= total_trades)
+    paginated_trades = all_trades[start_idx:end_idx] if start_idx < total_trades else []
     
     return {
         "backtest_id": run_id,
-        "trades": trades,
-        "total_trades": len(trades),
+        "trades": paginated_trades,
+        "total_trades": total_trades,
+        "page": page,
+        "per_page": per_page,
+        "total_pages": total_pages,
+        "has_next": page < total_pages,
+        "has_prev": page > 1,
     }
 
 @router.get("/bots/{bot_id}/backtests", response_model=List[BacktestResponse])

src/frontend/src/lib/api/client.ts

@@ -169,8 +169,16 @@ export const api = {
 			}
 		},
 
-		async getTrades(botId: string, runId: string): Promise<{ trades: any[]; total_trades: number }> {
-			const response = await fetch(`${API_URL}/bots/${botId}/backtest/${runId}/trades`, {
+		async getTrades(botId: string, runId: string, page: number = 1, perPage: number = 5): Promise<{
+			trades: any[];
+			total_trades: number;
+			page: number;
+			per_page: number;
+			total_pages: number;
+			has_next: boolean;
+			has_prev: boolean;
+		}> {
+			const response = await fetch(`${API_URL}/bots/${botId}/backtest/${runId}/trades?page=${page}&per_page=${perPage}`, {
 				headers: getAuthHeaders()
 			});
 			if (!response.ok) {

src/frontend/src/lib/api/types.ts

@@ -89,6 +89,26 @@ export interface BacktestResult {
 	sharpe_ratio: number;
 }
 
+export interface PaginatedTrades {
+	trades: Trade[];
+	total_trades: number;
+	page: number;
+	per_page: number;
+	total_pages: number;
+	has_next: boolean;
+	has_prev: boolean;
+}
+
+export interface Trade {
+	type: 'buy' | 'sell';
+	token: string;
+	price: number;
+	amount: number;
+	quantity: number;
+	timestamp: number;
+	exit_reason?: 'stop_loss' | 'take_profit' | string;
+}
+
 export interface Simulation {
 	id: string;
 	bot_id: string;

src/frontend/src/routes/bot/[id]/backtest/+page.svelte

@@ -19,6 +19,11 @@
 	// Expandable trades state
 	let expandedTrades = $state<Set<string>>(new Set());
 	
+	// Pagination state for each backtest
+	let tradesPage = $state<Record<string, number>>({});
+	let tradesData = $state<Record<string, any>>({});
+	const TRADES_PER_PAGE = 5;
+	
 	onMount(async () => {
 		// Set default dates - yesterday only (1 day range for fast testing)
 		const yesterday = new Date();
@@ -132,9 +137,37 @@
 			expandedTrades.delete(backtestId);
 		} else {
 			expandedTrades.add(backtestId);
+			// Load first page of trades if not loaded
+			if (!tradesData[backtestId]) {
+				loadTrades(backtestId, 1);
+			}
 		}
 		expandedTrades = new Set(expandedTrades);  // Trigger reactivity
 	}
+	
+	async function loadTrades(backtestId: string, page: number) {
+		try {
+			const data = await api.backtest.getTrades(botId, backtestId, page, TRADES_PER_PAGE);
+			tradesData[backtestId] = { ...data, currentPage: page };
+			tradesData = { ...tradesData };  // Trigger reactivity
+		} catch (e) {
+			console.error('Failed to load trades:', e);
+		}
+	}
+	
+	function nextTradesPage(backtestId: string) {
+		const data = tradesData[backtestId];
+		if (data && data.has_next) {
+			loadTrades(backtestId, data.page + 1);
+		}
+	}
+	
+	function prevTradesPage(backtestId: string) {
+		const data = tradesData[backtestId];
+		if (data && data.has_prev) {
+			loadTrades(backtestId, data.page - 1);
+		}
+	}
 </script>
 
 <svelte:head>
@@ -244,8 +277,21 @@
 									</button>
 									{#if expandedTrades.has(backtest.id)}
 										<div class="trades-inline">
+											{#if tradesData[backtest.id]}
+												<div class="trades-pagination-header">
+													<span class="trades-count">
+														Showing {((tradesData[backtest.id].page - 1) * TRADES_PER_PAGE) + 1}-{Math.min(tradesData[backtest.id].page * TRADES_PER_PAGE, tradesData[backtest.id].total_trades)} of {tradesData[backtest.id].total_trades}
+													</span>
+													{#if tradesData[backtest.id].total_pages > 1}
+														<div class="pagination-controls">
+															<button class="btn-pagination" onclick={() => prevTradesPage(backtest.id)} disabled={!tradesData[backtest.id].has_prev}>← Prev</button>
+															<span class="page-indicator">Page {tradesData[backtest.id].page} of {tradesData[backtest.id].total_pages}</span>
+															<button class="btn-pagination" onclick={() => nextTradesPage(backtest.id)} disabled={!tradesData[backtest.id].has_next}>Next →</button>
+														</div>
+													{/if}
+												</div>
 												<div class="trades-list">
-												{#each backtest.result.trades as trade}
+													{#each tradesData[backtest.id].trades as trade}
 														<div class="trade-item">
 															<span class="trade-type" class:buy={trade.type === 'buy'} class:sell={trade.type === 'sell'}>
 																{trade.type.toUpperCase()}
@@ -256,6 +302,9 @@
 														</div>
 													{/each}
 												</div>
+											{:else}
+												<div class="trades-loading">Loading trades...</div>
+											{/if}
 										</div>
 									{/if}
 								{/if}
@@ -784,4 +833,61 @@
 		background: rgba(255, 255, 255, 0.2);
 		color: #fff;
 	}
+
+	/* Pagination styles */
+	.trades-pagination-header {
+		display: flex;
+		justify-content: space-between;
+		align-items: center;
+		margin-bottom: 0.75rem;
+		padding-bottom: 0.5rem;
+		border-bottom: 1px solid rgba(255, 255, 255, 0.1);
+	}
+
+	.trades-count {
+		font-size: 0.85rem;
+		color: #888;
+	}
+
+	.pagination-controls {
+		display: flex;
+		align-items: center;
+		gap: 0.5rem;
+	}
+
+	.btn-pagination {
+		width: auto;
+		padding: 0.35rem 0.75rem;
+		background: rgba(102, 126, 234, 0.1);
+		border: 1px solid rgba(102, 126, 234, 0.3);
+		border-radius: 6px;
+		color: #667eea;
+		font-size: 0.8rem;
+		cursor: pointer;
+		transition: all 0.2s;
+	}
+
+	.btn-pagination:hover:not(:disabled) {
+		background: rgba(102, 126, 234, 0.2);
+		transform: none;
+	}
+
+	.btn-pagination:disabled {
+		opacity: 0.4;
+		cursor: not-allowed;
+	}
+
+	.page-indicator {
+		font-size: 0.8rem;
+		color: #888;
+		min-width: 80px;
+		text-align: center;
+	}
+
+	.trades-loading {
+		text-align: center;
+		color: #888;
+		padding: 1rem;
+		font-size: 0.9rem;
+	}
 </style>