feat: add SSH commit signing to git identities

Configure commit signing per Git identity
Apply SSH signing settings automatically
Support signing in web and VS Code

packages/ui/src/lib/api/types.ts

@@ -296,6 +296,8 @@ export interface GitIdentityProfile {
   userEmail: string;
   authType?: GitIdentityAuthType;
   sshKey?: string | null;
+  signCommits?: boolean;
+  signingKey?: string | null;
   host?: string | null;
   color?: string | null;
   icon?: string | null;