feat(helpdesk): add handover protocol management

Implement handover protocols as a new entity in the helpdesk module,
allowing users to create fillable protocol records from admin-defined
software product schemas.

Key additions:
- DB migration (helpdesk_handovers table) with tenant scope
- HandoverService with status workflow (draft/in_progress/completed/archived)
- Three-tier permissions (view/create/manage)
- Two-step creation wizard (Stripe-style assistant)
- Grid.js list page with search and status filter
- Edit/detail page with aside metadata and status controls
- Reusable core autocomplete lookup component (app-lookup-field)
- Debitor lookup data endpoint for autocomplete
- Dynamic form rendering from schema snapshots
- 11 PHPUnit tests for HandoverService
- DE+EN i18n translations (48 keys each)

Also includes: PHPStan fixes (dead code removal, stale baseline cleanup),
software product edit title improvement, fieldset simplification,
and Stripe-style hover for schema preview.

Workflow: HD-HANDOVERS-001 (.agents/runs/HD-HANDOVERS-001/)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

modules/helpdesk/migrations/005_create_handovers.sql

@@ -0,0 +1,19 @@
+CREATE TABLE IF NOT EXISTS `helpdesk_handovers` (
+    `id`              BIGINT UNSIGNED  NOT NULL AUTO_INCREMENT,
+    `tenant_id`       INT UNSIGNED     NOT NULL,
+    `debitor_no`      VARCHAR(30)      NOT NULL,
+    `debitor_name`    VARCHAR(255)     NOT NULL DEFAULT '',
+    `product_code`    VARCHAR(30)      NOT NULL,
+    `status`          VARCHAR(20)      NOT NULL DEFAULT 'draft',
+    `schema_snapshot` TEXT             NULL     DEFAULT NULL,
+    `field_values`    TEXT             NULL     DEFAULT NULL,
+    `created_by`      INT UNSIGNED     NOT NULL,
+    `updated_by`      INT UNSIGNED     NULL     DEFAULT NULL,
+    `created_at`      DATETIME         NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    `updated_at`      DATETIME         NULL     DEFAULT NULL ON UPDATE CURRENT_TIMESTAMP,
+    PRIMARY KEY (`id`),
+    KEY `idx_hh_tenant`  (`tenant_id`),
+    KEY `idx_hh_debitor` (`tenant_id`, `debitor_no`),
+    KEY `idx_hh_product` (`tenant_id`, `product_code`),
+    KEY `idx_hh_status`  (`tenant_id`, `status`)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;