feat(invites): team invite links — admin create/revoke, public accept (#42)

* feat(branding): white-label — public /branding, admin write, shell theming

app_settings branding.* keys (product name, logo/favicon URLs, accent
color, docs/support links). Public GET /branding so login and shell
theme pre-auth; admin writes via PUT /settings.

useBranding() applies document.title, accent CSS var and favicon;
BrandWordmark replaces hardcoded wordmarks; admin Platform settings
gain a Branding form. MCP containr_branding_get + settings_update.

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

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

* feat(invites): team invite links — admin create/revoke, public accept

Admins mint single-use invite links (sha256-hashed token at rest,
optional email binding, configurable TTL). Public endpoints let the
accept page validate the link and register — working even while
public signup is disabled.

- migration + sqlc queries/model for user_invites
- POST /admin/invites (returns one-time token+url), GET list, DELETE revoke
- GET /auth/invites/:token public validation, POST /auth/accept-invite
- CLI containr invites list|create|revoke; MCP invites tools
- /auth/accept-invite page (expired/used/invalid states, bound-email lock)
- Admin page Team invites section: create, copy link, revoke
- OpenAPI + generated types + CLI guide

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/mcpserver/server.go

@@ -158,6 +158,10 @@ func init() {
 	register(spec{"containr_branding_get", "Get instance white-label branding (product name, logo, accent, links).", "GET", "/branding", nil, nil, false})
 	register(spec{"containr_settings_update", "Update platform settings (admin). Args: signup_enabled (bool), cloudflare_tunnel_token (string, empty clears), branding (object: product_name, logo_url, favicon_url, accent_color, docs_url, support_url — empty string resets a field).", "PUT", "/settings", nil, []string{"signup_enabled", "cloudflare_tunnel_token", "branding"}, false})
 
+	register(spec{"containr_invites_list", "List team invite links (admin).", "GET", "/admin/invites", nil, nil, false})
+	register(spec{"containr_invites_create", "Create a team invite link (admin). Args: email (optional bind), expires_in_hours (default 168). Returns the one-time token + accept URL.", "POST", "/admin/invites", nil, []string{"email", "expires_in_hours"}, false})
+	register(spec{"containr_invites_revoke", "Revoke a team invite (admin). Args: id. Requires confirm=true.", "DELETE", "/admin/invites/{id}", []string{"id"}, nil, true})
+
 	// Nodes / agent tokens (admin)
 	register(spec{"containr_nodes_list", "List node agents (admin)", "GET", "/agents", nil, nil, false})
 	register(spec{"containr_nodes_get", "Get a node agent (admin)", "GET", "/agents/{id}", []string{"id"}, nil, false})