fix: Use proper chromedp options for no-sandbox mode

- Replace chromedp.Flag() with chromedp.NoSandbox
- Replace chromedp.Flag() with chromedp.DisableGPU
- Apply fix to both GenerateFromURL and GenerateFromURLWithOptions
- Fixes Ubuntu 23.10+ AppArmor sandbox restrictions

The chromedp.Flag() method wasn't properly disabling the sandbox, causing
Chrome to crash with 'No usable sandbox!' fatal error in CI.

internal/pdf/generator.go

@@ -34,10 +34,8 @@ func (g *Generator) GenerateFromURL(ctx context.Context, url string) ([]byte, er
 
 	// Create chromedp options for headless mode (especially for CI environments)
 	opts := append(chromedp.DefaultExecAllocatorOptions[:],
-		chromedp.Flag("headless", true),
+		chromedp.NoSandbox,
-		chromedp.Flag("disable-gpu", true),
+		chromedp.DisableGPU,
-		chromedp.Flag("no-sandbox", true),
-		chromedp.Flag("disable-dev-shm-usage", true),
 	)
 
 	// Create exec allocator with custom options
@@ -114,8 +112,18 @@ func (g *Generator) GenerateFromURLWithOptions(ctx context.Context, url string,
 	ctx, cancel := context.WithTimeout(ctx, g.timeout)
 	defer cancel()
 
+	// Create chromedp options for headless mode (especially for CI environments)
+	opts := append(chromedp.DefaultExecAllocatorOptions[:],
+		chromedp.NoSandbox,
+		chromedp.DisableGPU,
+	)
+
+	// Create exec allocator with custom options
+	execCtx, execCancel := chromedp.NewExecAllocator(ctx, opts...)
+	defer execCancel()
+
 	// Create chromedp context
-	allocCtx, allocCancel := chromedp.NewContext(ctx)
+	allocCtx, allocCancel := chromedp.NewContext(execCtx)
 	defer allocCancel()
 
 	// Buffer to store PDF