feat: add onboarding info fields to first user setup (#23989)

Add optional demographic and newsletter preference fields to the setup
page: business use (yes/no), industry type, organization size, and two
newsletter toggles (marketing, release/security updates).

The new data flows through telemetry via a FirstUserOnboarding struct in
the snapshot payload, sent once when the first user is created. The
telemetry-server and BigQuery schema changes are required separately to
persist this data.

---------

Co-authored-by: default <davidiii@fraley.us>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

coderd/telemetry/telemetry.go

@@ -1502,6 +1502,7 @@ type Snapshot struct {
 	PrebuiltWorkspaces                   []PrebuiltWorkspace                   `json:"prebuilt_workspaces"`
 	AIBridgeInterceptionsSummaries       []AIBridgeInterceptionsSummary        `json:"aibridge_interceptions_summaries"`
 	BoundaryUsageSummary                 *BoundaryUsageSummary                 `json:"boundary_usage_summary"`
+	FirstUserOnboarding                  *FirstUserOnboarding                  `json:"first_user_onboarding"`
 }
 
 // Deployment contains information about the host running Coder.
@@ -1551,6 +1552,18 @@ type User struct {
 	LoginType string `json:"login_type,omitempty"`
 }
 
+// FirstUserOnboarding contains optional demographic and newsletter
+// preference data collected during first user setup. This is sent
+// once when the first user is created. Pointer fields distinguish an
+// explicit answer from a skipped question.
+type FirstUserOnboarding struct {
+	IsBusiness          *bool  `json:"is_business"`
+	IndustryType        string `json:"industry_type"`
+	OrgSize             string `json:"org_size"`
+	NewsletterMarketing *bool  `json:"newsletter_marketing"`
+	NewsletterReleases  *bool  `json:"newsletter_releases"`
+}
+
 type Group struct {
 	ID             uuid.UUID            `json:"id"`
 	Name           string               `json:"name"`