Fix BASE_URL config loading, add tasks/projects; robust .env path resolution

- Config: try ENV_FILE, .env, ../.env for loading; trim trailing slash from BaseURL
- Log BASE_URL at server startup for verification
- .env.example: document BASE_URL
- Tasks, projects, tags, migrations and related API/handlers

Made-with: Cursor

internal/utils/pgtype.go

@@ -100,6 +100,13 @@ func NullPgUUID() pgtype.UUID {
 	return pgtype.UUID{Valid: false}
 }
 
+func ToPgUUIDPtr(id *uuid.UUID) pgtype.UUID {
+	if id == nil {
+		return pgtype.UUID{Valid: false}
+	}
+	return pgtype.UUID{Bytes: *id, Valid: true}
+}
+
 func NullPgTimestamptz() pgtype.Timestamptz {
 	return pgtype.Timestamptz{Valid: false}
 }