hub v0.39.0: offsite hardening — F4 credential re-issue, F2 scan retry, F5 save UX

F4: ReissueCredentials — explicit operator recovery for consumed-password
dead-ends; resets the labelled resource's password (exactly-1 guard,
red-proofed), stores a fresh one-time secret, bumps ConfigVersion.
New hetznerapi.ResetBoxPassword for the dedicated path.
F2: host-key scan retry-with-backoff (~60s ladder, red-proofed) — first
save survives fresh-subaccount DNS lag.
F5: config form disables submits + shows an in-flight notice (the re-click
bait that caused live F1).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PSK5g6qYLknKj8u3QAFEr6

hub/internal/hetznerapi/hetznerapi.go

@@ -96,6 +96,7 @@ type CloudAPI interface {
 	GetStorageBox(ctx context.Context, boxID int64) (StorageBox, error)
 	CreateStorageBox(ctx context.Context, req CreateBoxRequest) (createdID int64, action Action, err error)
 	ChangeType(ctx context.Context, boxID int64, boxType string) (Action, error)
+	ResetBoxPassword(ctx context.Context, boxID int64, password string) (Action, error)
 	DeleteStorageBox(ctx context.Context, boxID int64) (Action, error)
 
 	// WaitAction polls the action to "success" (bounded); errors on "error" or timeout.
@@ -270,6 +271,16 @@ func (c *Client) ChangeType(ctx context.Context, boxID int64, boxType string) (A
 	return out.Action, err
 }
 
+// ResetBoxPassword resets a dedicated box's (main-account) password. The password value is only ever in
+// the request body — never logged by the caller (F4 re-issue).
+func (c *Client) ResetBoxPassword(ctx context.Context, boxID int64, password string) (Action, error) {
+	var out struct {
+		Action Action `json:"action"`
+	}
+	err := c.do(ctx, http.MethodPost, fmt.Sprintf("/storage_boxes/%d/actions/reset_password", boxID), map[string]string{"password": password}, &out)
+	return out.Action, err
+}
+
 func (c *Client) DeleteStorageBox(ctx context.Context, boxID int64) (Action, error) {
 	var out struct {
 		Action Action `json:"action"`