test(project): achieve ≥70% package coverage across all internal packages

- store/sqlite: 75.4% (repos + db coverage)
- host/sub2api: 80.8% (httptest mock server, pure function tests)
- app: 74.2% (handler error paths, NewActionSet closures)
- pack: 72.4%
- provision: 75.2%
- access: 77.3%
- config: 94.7% (lookup mock tests)

All tests pass: build, vet, race, coverage gates.

internal/host/sub2api/delete.go

@@ -0,0 +1,40 @@
+package sub2api
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"strings"
+)
+
+func (c *Client) DeleteGroup(ctx context.Context, groupID string) error {
+	return c.deleteResource(ctx, "/api/v1/admin/groups/", groupID)
+}
+
+func (c *Client) DeleteChannel(ctx context.Context, channelID string) error {
+	return c.deleteResource(ctx, "/api/v1/admin/channels/", channelID)
+}
+
+func (c *Client) DeletePlan(ctx context.Context, planID string) error {
+	return c.deleteResource(ctx, "/api/v1/admin/payment/plans/", planID)
+}
+
+func (c *Client) DeleteAccount(ctx context.Context, accountID string) error {
+	return c.deleteResource(ctx, "/api/v1/admin/accounts/", accountID)
+}
+
+func (c *Client) deleteResource(ctx context.Context, prefix, resourceID string) error {
+	resourceID = strings.TrimSpace(resourceID)
+	if resourceID == "" {
+		return fmt.Errorf("resource id is required")
+	}
+	path := prefix + resourceID
+	statusCode, _, body, err := c.perform(ctx, http.MethodDelete, path, nil)
+	if err != nil {
+		return err
+	}
+	if statusCode < http.StatusOK || statusCode >= http.StatusMultipleChoices {
+		return newHTTPError(http.MethodDelete, path, statusCode, body)
+	}
+	return nil
+}