Feat default surface routing + fix startup hang (#4)

Default surface routing (v0.2.1):
- `/` redirects to configurable default surface with fallback chain:
  configured → first enabled extension surface → /admin
- Auto-sets default_surface on first extension surface install
- Admin settings UI: Default Surface dropdown
- disabledRedirect() and extension surface disabled redirect now go to
  /admin instead of / to prevent redirect loops

Fix Gin route param conflict causing backend startup hang:
- Team package settings routes used `:pkgId` while sibling routes used
  `:id` — Gin's radix tree entered infinite loop on conflicting param
  names. Unified to `:id`.

Docker entrypoint hardening:
- Health check timeout 10s → 60s
- Stale backend process cleanup on restart
- Crash detection (exit early if backend dies)

Roadmap direction updates:
- v0.3.0: Notes surface (Obsidian-style) replaces Editor surface
- v0.4.0: MVP (was v0.5.0) — chat moved to post-MVP
- No built-in auto-install — explicit install only

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

server/handlers/packages.go

@@ -553,6 +553,18 @@ func (h *PackageHandler) InstallPackage(c *gin.Context) {
 		log.Printf("[packages] %s: %d dependencies recorded", pkgID, len(deps))
 	}
 
+	// v0.2.1: Auto-set default_surface when the first extension surface is installed.
+	if (pkgType == "surface" || pkgType == "full") && pkgSource != "core" {
+		if raw, err := h.stores.GlobalConfig.Get(c.Request.Context(), "default_surface"); err != nil || raw == nil {
+			dflt := models.JSONMap{"id": pkgID}
+			if setErr := h.stores.GlobalConfig.Set(c.Request.Context(), "default_surface", dflt, ""); setErr != nil {
+				log.Printf("[packages] failed to auto-set default_surface to %s: %v", pkgID, setErr)
+			} else {
+				log.Printf("[packages] Auto-set default_surface to %s (first extension surface)", pkgID)
+			}
+		}
+	}
+
 	c.JSON(http.StatusOK, gin.H{
 		"id":      pkgID,
 		"title":   title,