Orgs: let any user create an organization and become its admin

Organization writes were superadmin-only, so standing up a tenant needed
an out-of-band superadmin. Creating one is now self-service, and an admin
manages the org they belong to.

- POST /api/orgs is open to any authenticated user. A creator who isn't a
  superadmin must have no organization yet (a single-valued membership
  relation means a second one would abandon the first), and is promoted to
  the new org's admin and first member in the same request. If that
  promotion fails the org is rolled back, so it is never left stranded
  with nobody able to administer it. Superadmins still create tenants
  without joining them.
- PATCH/DELETE are manager-gated and scope an admin to their own org. An
  admin deletes theirs only as its sole member: they are detached and
  demoted to a plain user before the record goes, so the org is empty when
  it is removed. Other members still block deletion with a 409.
- /api/me now carries organization + organizationName, which the clients
  need to tell "no org yet" from "org you administer".

The panel, Web App (new OrgManager.vue in Settings) and Phone App (new
_OrganizationSection) all mirror the server's gates rather than
re-deciding them. The Phone App cached its role at login and gates the
Users tab on it, so AuthService.adoptRole refreshes that from the profile
instead of making a freshly promoted admin sign in again.

Covered by orgs_test.go, which drives the real handler + middleware chain
against a stand-in PocketBase: promotion, the already-a-member refusal,
superadmin staying unattached, the rollback, own-org scoping, the
detach-and-demote, and the blocking-member 409.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

API Server/internal/api/server.go

@@ -28,7 +28,7 @@
 //	GET    /api/me/export              POST   /api/me/import
 //	POST   /api/me/delete              POST   /api/me/delete/cancel
 //
-//	# users + organizations (manager; writes to orgs are superadmin-only)
+//	# users + organizations (manager; POST /api/orgs is open to any user)
 //	GET    /api/users                  POST   /api/users
 //	PATCH  /api/users/{id}             DELETE /api/users/{id}
 //	GET    /api/orgs                   POST   /api/orgs
@@ -285,12 +285,15 @@ func (s *Server) Handler() http.Handler {
 	mux.HandleFunc("PATCH /api/users/{id}", s.requireManager(s.handleUpdateUser))
 	mux.HandleFunc("DELETE /api/users/{id}", s.requireManager(s.handleDeleteUser))
 
-	// Organizations — listing is manager-scoped; create/edit/delete are
-	// superadmin-only (a superadmin spans all organizations).
+	// Organizations — the tenants users belong to. Listing is manager-scoped (an
+	// admin sees only their own org). Any org-less user may create an org and
+	// becomes its admin; an admin may rename or delete their own org; a superadmin
+	// spans every organization. Create carries no role gate, so it checks the
+	// service account itself.
 	mux.HandleFunc("GET /api/orgs", s.requireManager(s.handleListOrgs))
-	mux.HandleFunc("POST /api/orgs", s.requireSuperadmin(s.handleCreateOrg))
-	mux.HandleFunc("PATCH /api/orgs/{id}", s.requireSuperadmin(s.handleUpdateOrg))
-	mux.HandleFunc("DELETE /api/orgs/{id}", s.requireSuperadmin(s.handleDeleteOrg))
+	mux.HandleFunc("POST /api/orgs", s.handleCreateOrg)
+	mux.HandleFunc("PATCH /api/orgs/{id}", s.requireManager(s.handleUpdateOrg))
+	mux.HandleFunc("DELETE /api/orgs/{id}", s.requireManager(s.handleDeleteOrg))
 
 	// PocketBase connection settings — superadmin only. These do NOT require the
 	// service account to already be configured (they exist to configure it).