Add granular logging across all source files

Introduce logger infrastructure and add structured logging to every layer:
alpaca.ts (buy/sell/quote/clock), momentum-indicator.ts (evaluate flow),
momentum-strategy.ts (poll loop), index.ts (startup/cycle), and trading.ts
(market timing). Replace raw console.log calls with leveled logger. Update
all tests with appropriate console spies.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/momentum-indicator.ts

@@ -1,5 +1,6 @@
 import { Alpaca } from "./alpaca";
 import { Indicator } from "./indicator";
+import { logger } from "./logger";
 import { wait } from "./trading";
 
 export interface MomentumResult {
@@ -29,15 +30,17 @@ export class MomentumIndicator implements Indicator<MomentumResult> {
     }
 
     async evaluate(alpaca: Alpaca): Promise<MomentumResult> {
+        logger.debug(`waiting ${this.config.settleDelay}ms for market to settle`);
         await wait(this.config.settleDelay);
 
         const priceBefore = await alpaca.getLatestAsk(this.config.symbol);
-        
+        logger.debug(`${this.config.symbol} priceBefore: ${priceBefore}`);
+
         await wait(this.config.sampleDelay);
 
         const priceAfter = await alpaca.getLatestAsk(this.config.symbol);
-        
         const direction = priceAfter >= priceBefore ? 'up' : 'down';
+        logger.debug(`${this.config.symbol} priceAfter: ${priceAfter} → direction: ${direction}`);
 
         return { direction, priceBefore, priceAfter };
     }