fix(db): add close_reason column to issues table (bd-uyu)

- Add migration 017_close_reason_column.go to create the column
- Update all INSERT statements to include close_reason
- Update all SELECT statements to include close_reason
- Update doctor.go to check for close_reason in schema validation
- Remove workaround code that batch-loaded close reasons from events table
- Fix migrations_test.go to include close_reason in test table schema

This fixes sync loops where close_reason values were silently dropped
because the DB lacked the column despite the struct having the field.

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

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

cmd/bd/doctor.go

@@ -1780,7 +1780,7 @@ func checkSchemaCompatibility(path string) doctorCheck {
 	// This is a simplified version since we can't import the internal package directly
 	// Check all critical tables and columns
 	criticalChecks := map[string][]string{
-		"issues":         {"id", "title", "content_hash", "external_ref", "compacted_at"},
+		"issues":         {"id", "title", "content_hash", "external_ref", "compacted_at", "close_reason"},
 		"dependencies":   {"issue_id", "depends_on_id", "type"},
 		"child_counters": {"parent_id", "last_child"},
 		"export_hashes":  {"issue_id", "content_hash"},