feat(setup): first-run wizard — admin, GitHub App, tunnel, done (#71)

* feat(setup): first-run wizard — admin, GitHub App, tunnel, done

- GET /api/v1/setup/status (public): has_users, needs_setup,
  has_github_app, has_tunnel. app_settings.setup_completed flag; installs
  with existing projects auto-complete so upgrades never see the wizard.
- POST /api/v1/setup/complete records the flag.
- /setup page: progress rail + four steps — create admin (links into the
  bootstrap sign-up with redirect back), GitHub App manifest flow,
  optional Cloudflare tunnel token, finish. Every optional step is
  skippable; nothing blocks.
- PlatformShell redirects signed-in users to /setup while needs_setup.
- The GitHub App callback honors a sessionStorage return marker set by
  the wizard so provisioning resumes at /setup instead of /settings.
- OpenAPI documents both endpoints.

Verified live: status reports auto-completed on this install,
complete persists the flag, response shape matches the client.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

* test(setup): wizard step-state coverage

Five cases across the state machine: fresh-install account prompt,
sign-in resume, git-provider step, tunnel step, and finish.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

---------

Co-authored-by: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

app/backend/internal/api/routes.go

@@ -286,6 +286,7 @@ func SetupRoutes(router *gin.Engine, db *database.DB, redis *database.Redis, cfg
 			public.POST("/auth/register", handleRegister)
 			public.GET("/maintenance", handleMaintenancePage)
 			public.GET("/branding", handleGetBranding)
+			public.GET("/setup/status", handleSetupStatus)
 
 			// Invite accept flow — validates the link, then registers
 			// even while public signup is closed.
@@ -355,6 +356,7 @@ func SetupRoutes(router *gin.Engine, db *database.DB, redis *database.Redis, cfg
 		{
 			authed.GET("/user/profile", handleGetProfile)
 			authed.PUT("/user/profile", handleUpdateProfile)
+			authed.POST("/setup/complete", handleSetupComplete)
 
 			// Personal access tokens for CLI/MCP/agent auth.
 			authed.GET("/user/tokens", handleListUserTokens)

app/backend/internal/api/setup.go

@@ -0,0 +1,78 @@
+package api
+
+// First-run setup wizard state. GET /setup/status is public so the web
+// shell can redirect fresh installs before a session exists; the flag
+// lives in app_settings so it survives restarts.
+
+import (
+	"net/http"
+	"strings"
+
+	"containr/internal/database"
+
+	"github.com/gin-gonic/gin"
+)
+
+const settingSetupCompleted = "setup_completed"
+
+// setupComplete resolves the flag. Installs that predate the wizard
+// (users + projects already exist) auto-complete — nobody who has been
+// running Containr for months should get a welcome screen.
+func setupComplete(db *database.DB, hasUsers bool) bool {
+	if strings.EqualFold(settingValue(db, settingSetupCompleted, "", ""), "true") {
+		return true
+	}
+	if !hasUsers {
+		return false
+	}
+	var projects int
+	if err := db.QueryRow(`SELECT COUNT(*) FROM projects`).Scan(&projects); err == nil && projects > 0 {
+		return true
+	}
+	return false
+}
+
+// GET /api/v1/setup/status — public: fresh installs hit it before any
+// session exists.
+func handleSetupStatus(c *gin.Context) {
+	db, ok := c.MustGet("db").(*database.DB)
+	if !ok {
+		respondError(c, http.StatusInternalServerError, "INTERNAL_ERROR", "Database connection not available")
+		return
+	}
+	count, err := countLocalUsers(db)
+	if err != nil {
+		respondError(c, http.StatusInternalServerError, "INTERNAL_ERROR", "Failed to inspect setup state")
+		return
+	}
+	hasUsers := count > 0
+	completed := setupComplete(db, hasUsers)
+	tunnelToken, _ := resolvedTunnelToken(db)
+	c.JSON(http.StatusOK, gin.H{
+		"has_users":       hasUsers,
+		"setup_completed": completed,
+		"needs_setup":     !completed,
+		"has_github_app":  githubAppConfigured(db),
+		"has_tunnel":      tunnelToken != "",
+		"signup_enabled":  signupEnabled(db),
+	})
+}
+
+// POST /api/v1/setup/complete — marks the wizard done. Open to any
+// authenticated user: the first account is the owner, and the flag only
+// suppresses a banner.
+func handleSetupComplete(c *gin.Context) {
+	if _, ok := requireAuthenticatedUserID(c); !ok {
+		return
+	}
+	db, ok := c.MustGet("db").(*database.DB)
+	if !ok {
+		respondError(c, http.StatusInternalServerError, "INTERNAL_ERROR", "Database connection not available")
+		return
+	}
+	if err := setSetting(db, settingSetupCompleted, "true", false); err != nil {
+		respondError(c, http.StatusInternalServerError, "INTERNAL_ERROR", "Failed to save setup state")
+		return
+	}
+	c.JSON(http.StatusOK, gin.H{"message": "Setup completed"})
+}