refactor: implement worker pool pattern, add persistent task queue, and decouple target loading logic

internal/filter/filter.go

@@ -21,14 +21,17 @@ func NewPipeline(filters ...JobFilter) *FilterPipeline {
 	return &FilterPipeline{filters: filters}
 }
 
-func (p *FilterPipeline) Execute(ctx context.Context, title, rawContent string) (bool, float64) {
+func (p *FilterPipeline) Execute(ctx context.Context, title, rawContent string) (bool, float64, string) {
 	var totalScore float64
 	for _, f := range p.filters {
 		res, err := f.Process(ctx, title, rawContent)
-		if err != nil || !res.Keep {
-			return false, 0
+		if err != nil {
+			return false, 0, err.Error()
+		}
+		if !res.Keep {
+			return false, 0, res.Reason
 		}
 		totalScore += res.Score
 	}
-	return true, totalScore
+	return true, totalScore, ""
 }

internal/filter/filter_test.go

@@ -39,7 +39,7 @@ func TestFilterPipeline(t *testing.T) {
 	pipeline := NewPipeline(hardFilter, scoringFilter)
 
 	// Test job 1: Unpaid job -> rejected by hard filter
-	keep1, score1 := pipeline.Execute(ctx, "Backend Intern", "Unpaid position working with Go.")
+	keep1, score1, _ := pipeline.Execute(ctx, "Backend Intern", "Unpaid position working with Go.")
 	if keep1 {
 		t.Errorf("expected job 1 to be filtered out, got keep=true")
 	}
@@ -48,7 +48,7 @@ func TestFilterPipeline(t *testing.T) {
 	}
 
 	// Test job 2: Qualified job -> passes both filters and accumulates score
-	keep2, score2 := pipeline.Execute(ctx, "Senior Go Backend Engineer", "Building high throughput services.")
+	keep2, score2, _ := pipeline.Execute(ctx, "Senior Go Backend Engineer", "Building high throughput services.")
 	if !keep2 {
 		t.Errorf("expected job 2 to pass filter pipeline, got keep=false")
 	}