Fix the MQTT node, suggest message names, and drop Items

- MQTT nodes failed to build: the topic map was renamed to talk in ports, but
  __slots__ still declared the old name, so every MQTT node raised
  AttributeError. Building one of each node type is now a test, since __slots__
  makes this failure invisible until someone places the node.
- Port names offer the messages already in play: everything published is worth
  reading, and an input nobody provides yet is worth publishing. A message only
  connects when both ends spell it the same way, so choosing beats typing.
- Adding a port focuses its name field.
- Dragging onto an input that already reads something offers the extra port as
  well as the replacement — an MQTT or InfluxDB node usually wants both.
- The template's Item model, its routes, screens and table are gone.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016WzrvW7rjQbynnhF6pxh6i

frontend/src/routeTree.gen.ts

@@ -17,7 +17,6 @@ import { Route as LayoutRouteImport } from './routes/_layout'
 import { Route as CanvasRouteImport } from './routes/_canvas'
 import { Route as LayoutIndexRouteImport } from './routes/_layout/index'
 import { Route as LayoutSettingsRouteImport } from './routes/_layout/settings'
-import { Route as LayoutItemsRouteImport } from './routes/_layout/items'
 import { Route as LayoutAdminRouteImport } from './routes/_layout/admin'
 import { Route as CanvasFlowsIndexRouteImport } from './routes/_canvas/flows/index'
 import { Route as CanvasFlowsFlowNameRouteImport } from './routes/_canvas/flows/$flowName'
@@ -60,11 +59,6 @@ const LayoutSettingsRoute = LayoutSettingsRouteImport.update({
   path: '/settings',
   getParentRoute: () => LayoutRoute,
 } as any)
-const LayoutItemsRoute = LayoutItemsRouteImport.update({
-  id: '/items',
-  path: '/items',
-  getParentRoute: () => LayoutRoute,
-} as any)
 const LayoutAdminRoute = LayoutAdminRouteImport.update({
   id: '/admin',
   path: '/admin',
@@ -88,7 +82,6 @@ export interface FileRoutesByFullPath {
   '/reset-password': typeof ResetPasswordRoute
   '/signup': typeof SignupRoute
   '/admin': typeof LayoutAdminRoute
-  '/items': typeof LayoutItemsRoute
   '/settings': typeof LayoutSettingsRoute
   '/flows/$flowName': typeof CanvasFlowsFlowNameRoute
   '/flows/': typeof CanvasFlowsIndexRoute
@@ -100,7 +93,6 @@ export interface FileRoutesByTo {
   '/reset-password': typeof ResetPasswordRoute
   '/signup': typeof SignupRoute
   '/admin': typeof LayoutAdminRoute
-  '/items': typeof LayoutItemsRoute
   '/settings': typeof LayoutSettingsRoute
   '/flows/$flowName': typeof CanvasFlowsFlowNameRoute
   '/flows': typeof CanvasFlowsIndexRoute
@@ -114,7 +106,6 @@ export interface FileRoutesById {
   '/reset-password': typeof ResetPasswordRoute
   '/signup': typeof SignupRoute
   '/_layout/admin': typeof LayoutAdminRoute
-  '/_layout/items': typeof LayoutItemsRoute
   '/_layout/settings': typeof LayoutSettingsRoute
   '/_layout/': typeof LayoutIndexRoute
   '/_canvas/flows/$flowName': typeof CanvasFlowsFlowNameRoute
@@ -129,7 +120,6 @@ export interface FileRouteTypes {
     | '/reset-password'
     | '/signup'
     | '/admin'
-    | '/items'
     | '/settings'
     | '/flows/$flowName'
     | '/flows/'
@@ -141,7 +131,6 @@ export interface FileRouteTypes {
     | '/reset-password'
     | '/signup'
     | '/admin'
-    | '/items'
     | '/settings'
     | '/flows/$flowName'
     | '/flows'
@@ -154,7 +143,6 @@ export interface FileRouteTypes {
     | '/reset-password'
     | '/signup'
     | '/_layout/admin'
-    | '/_layout/items'
     | '/_layout/settings'
     | '/_layout/'
     | '/_canvas/flows/$flowName'
@@ -228,13 +216,6 @@ declare module '@tanstack/react-router' {
       preLoaderRoute: typeof LayoutSettingsRouteImport
       parentRoute: typeof LayoutRoute
     }
-    '/_layout/items': {
-      id: '/_layout/items'
-      path: '/items'
-      fullPath: '/items'
-      preLoaderRoute: typeof LayoutItemsRouteImport
-      parentRoute: typeof LayoutRoute
-    }
     '/_layout/admin': {
       id: '/_layout/admin'
       path: '/admin'
@@ -274,14 +255,12 @@ const CanvasRouteWithChildren =
 
 interface LayoutRouteChildren {
   LayoutAdminRoute: typeof LayoutAdminRoute
-  LayoutItemsRoute: typeof LayoutItemsRoute
   LayoutSettingsRoute: typeof LayoutSettingsRoute
   LayoutIndexRoute: typeof LayoutIndexRoute
 }
 
 const LayoutRouteChildren: LayoutRouteChildren = {
   LayoutAdminRoute: LayoutAdminRoute,
-  LayoutItemsRoute: LayoutItemsRoute,
   LayoutSettingsRoute: LayoutSettingsRoute,
   LayoutIndexRoute: LayoutIndexRoute,
 }