Fix critical issues in WHOOSH Gitea issue monitoring and task creation

This commit resolves multiple blocking issues that were preventing WHOOSH from
properly detecting and converting bzzz-task labeled issues from Gitea:

## Issues Fixed:

1. **JSON Parsing Error**: Gitea API returns repository owner as string in issue
   responses, but code expected User object. Added IssueRepository struct to
   handle this API response format difference.

2. **Database Error Handling**: Code was using database/sql.ErrNoRows but
   system uses pgx driver. Updated imports and error constants to use
   pgx.ErrNoRows consistently.

3. **NULL Value Scanning**: Database fields (repository, project_id,
   estimated_hours, complexity_score) can be NULL but Go structs used
   non-pointer types. Added proper NULL handling with pointer scanning
   and safe conversion.

## Results:
- ✅ WHOOSH now successfully detects bzzz-task labeled issues
- ✅ Task creation pipeline working end-to-end
- ✅ Tasks API functioning properly
- ✅ First bzzz-task converted: "Logic around registered agents faulty"

The core issue monitoring workflow is now fully operational and ready for
CHORUS integration.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

internal/monitor/monitor.go

@@ -2,7 +2,6 @@ package monitor
 
 import (
 	"context"
-	"database/sql"
 	"encoding/json"
 	"fmt"
 	"strconv"
@@ -11,6 +10,7 @@ import (
 
 	"github.com/chorus-services/whoosh/internal/config"
 	"github.com/chorus-services/whoosh/internal/gitea"
+	"github.com/jackc/pgx/v5"
 	"github.com/jackc/pgx/v5/pgxpool"
 	"github.com/rs/zerolog/log"
 )
@@ -202,11 +202,14 @@ func (m *Monitor) syncRepository(ctx context.Context, repo RepositoryConfig) {
 // createOrUpdateTask creates a new task or updates an existing one from a Gitea issue
 func (m *Monitor) createOrUpdateTask(ctx context.Context, repo RepositoryConfig, issue gitea.Issue) (string, bool, error) {
 	// Check if task already exists
-	var existingTaskID sql.NullString
+	var existingTaskID string
 	query := `SELECT id FROM tasks WHERE external_id = $1 AND source_type = $2`
 	err := m.db.QueryRow(ctx, query, strconv.FormatInt(issue.Number, 10), repo.SourceType).Scan(&existingTaskID)
 	
-	if err != nil && err != sql.ErrNoRows {
+	taskExists := err == nil
+	
+	// Handle errors other than "no rows found"
+	if err != nil && err != pgx.ErrNoRows {
 		return "", false, fmt.Errorf("failed to check existing task: %w", err)
 	}
 	
@@ -230,8 +233,8 @@ func (m *Monitor) createOrUpdateTask(ctx context.Context, repo RepositoryConfig,
 	techStack := m.extractTechStackFromIssue(issue)
 	techStackJSON, _ := json.Marshal(techStack)
 	
-	if existingTaskID.Valid {
-		// Update existing task
+	if taskExists {
+		// Task exists - update it
 		updateQuery := `
 			UPDATE tasks SET
 				title = $1,
@@ -253,14 +256,14 @@ func (m *Monitor) createOrUpdateTask(ctx context.Context, repo RepositoryConfig,
 			labelsJSON,
 			techStackJSON,
 			issue.UpdatedAt,
-			existingTaskID.String,
+			existingTaskID,
 		)
 		
 		if err != nil {
 			return "", false, fmt.Errorf("failed to update task: %w", err)
 		}
 		
-		return existingTaskID.String, false, nil
+		return existingTaskID, false, nil
 	} else {
 		// Create new task
 		var taskID string
@@ -440,10 +443,10 @@ func (m *Monitor) getMonitoredRepositories(ctx context.Context) ([]RepositoryCon
 
 // updateRepositoryStatus updates the sync status of a repository
 func (m *Monitor) updateRepositoryStatus(ctx context.Context, repoID, status string, err error) error {
-	var errorMsg sql.NullString
+	var errorMsg *string
 	if err != nil {
-		errorMsg.String = err.Error()
-		errorMsg.Valid = true
+		errStr := err.Error()
+		errorMsg = &errStr
 	}
 	
 	query := `
@@ -555,7 +558,7 @@ func (m *Monitor) getRepositoryByID(ctx context.Context, repoID string) (*Reposi
 		&chorusLabelsJSON, &repo.LastSync, &repo.LastIssueSync, &repo.SyncStatus,
 	)
 	if err != nil {
-		if err == sql.ErrNoRows {
+		if err == pgx.ErrNoRows {
 			return nil, fmt.Errorf("repository not found: %s", repoID)
 		}
 		return nil, fmt.Errorf("failed to query repository: %w", err)