Add document approval workflow

Introduce a complete approval system for document publishing. Document
versions can now require approval from selected reviewers before being
published, with automatic publishing once all approvers have approved.

- Add approval quorum and decision tables with backfill migration
- Implement request approval, approve, and reject flows with electronic
  signature support for approve decisions
- Add employee approvals page with dedicated tab and pending approvals view
- Add changelog field to publish and request approval flows
- Pre-select previous version's approvers in the publish dialog
- Show quorum approvers in document list with 100 approver hard limit
- Expose approval workflow through GraphQL, MCP, and CLI
- Remove legacy default approvers feature entirely
- Add comprehensive e2e test coverage for approval workflows

Signed-off-by: Sacha Al Himdani <sacha@getprobo.com>

packages/emails/templates/document-approval.txt

@@ -0,0 +1,20 @@
+Probo
+
+Hi {{.RecipientFullName}},
+
+You're receiving this message because {{.OrganizationName}} has requested your approval on the document {{.DocumentName}}.
+
+Please take a moment to review the document and approve or reject it by clicking the link below:
+
+{{.ApprovalUrl}}
+
+If you have any questions, please contact your security team.
+
+This process is managed securely by Probo, acting as the compliance partner on behalf of {{.OrganizationName}}.
+
+Thank you for your prompt attention to this matter.
+
+Best regards,
+
+{{.SenderCompanyHeadquarterAddress}}
+Powered By Probo

packages/emails/templates/electronic-signature-certificate.txt

@@ -2,7 +2,7 @@
 
 Hi {{.RecipientFullName}},
 
-Your {{.DocumentType}} has been signed electronically. A Certificate of Completion is attached to this email as a PDF document.
+Your {{.DocumentName}} has been signed electronically. A Certificate of Completion is attached to this email as a PDF document.
 
 The certificate contains a complete record of the signing event, including the integrity seal, timestamp, and audit trail.