refactor: uniform validation, fix create form UX, dedupe filter dropdowns

- Remove dead registerValidator (Auth/register.ts), unused since signupValidator
  is the one actually wired to NewAccountController
- computers/create.vue: switch to useForm() + @submit.prevent so the form
  submits on Enter and shows a processing state, matching components/create.vue
- components/edit.vue: drop the 'origin' field, which was never provided by
  the backend (edit() never shared it) and therefore always undefined
- Extract FilterDropdown.vue and reuse it in ComponentsViewer/ComputersViewer,
  removing ~80 lines of duplicated dropdown markup/logic and fixing duplicate
  HTML ids (id="used" appeared twice in ComputersViewer)
- Move MIGRATION_*.md artifacts into docs/migration-history/

inertia/pages/computers/create.vue

@@ -1,11 +1,12 @@
 <script setup lang="ts">
-import { computed, reactive } from 'vue'
+import { computed } from 'vue'
 import { Link } from '@adonisjs/inertia/vue'
-import { usePage } from '@inertiajs/vue3'
+import { useForm, usePage } from '@inertiajs/vue3'
+import type { Component, ComputerState } from '~/pages/types/UITypes'
 
 const { props } = usePage<{
-  components: any[]
-  states: any[]
+  components: Component[]
+  states: ComputerState[]
   errors: Record<string, string>
 }>()
 const { components, states } = props
@@ -26,7 +27,7 @@ const componentTypeOrder = [
 ]
 
 const componentsByType = computed(() => {
-  const groups = new Map<string, any[]>()
+  const groups = new Map<string, Component[]>()
   components.forEach((component) => {
     if (!groups.has(component.type.name)) {
       groups.set(component.type.name, [])
@@ -38,21 +39,35 @@ const componentsByType = computed(() => {
     .sort((a, b) => componentTypeOrder.indexOf(a.type) - componentTypeOrder.indexOf(b.type))
 })
 
-const form = reactive({
+const form = useForm<{
+  title: string
+  sellPrice: number
+  gpuScore: number
+  cpuScore: number
+  stateId: number
+  globalScore: number
+  componentsId: number[]
+  pictures: Record<string, never>[]
+}>({
   title: '',
   sellPrice: 0,
   gpuScore: 0,
   cpuScore: 0,
   stateId: 1,
   globalScore: 0,
-  componentsId: [] as number[],
+  componentsId: [],
+  pictures: [],
 })
+
+function submitForm() {
+  form.post('/computers')
+}
 </script>
 
 <template>
   <div class="max-w-4xl mx-auto p-8 bg-white shadow-lg rounded-lg">
     <h1 class="text-2xl font-semibold mb-8 text-gray-800">Create New Computer</h1>
-    <form class="space-y-6">
+    <form class="space-y-6" @submit.prevent="submitForm">
       <div class="mt-2">
         <label class="block text-gray-700 text-sm font-bold mb-2" for="title">Title</label>
         <input
@@ -149,16 +164,21 @@ const form = reactive({
         </div>
       </div>
 
-      <Link
-        href="/computers"
-        type="button"
-        as="button"
-        method="post"
-        :data="form"
-        class="px-4 py-2 bg-indigo-600 text-white rounded hover:bg-blue-700 transition"
-      >
-        Create
-      </Link>
+      <div class="flex gap-4">
+        <button
+          type="submit"
+          :disabled="form.processing"
+          class="px-4 py-2 bg-indigo-600 text-white rounded hover:bg-indigo-700 transition disabled:opacity-50"
+        >
+          {{ form.processing ? 'Creating…' : 'Create' }}
+        </button>
+        <Link
+          href="/computers"
+          class="px-4 py-2 bg-gray-300 text-gray-800 rounded hover:bg-gray-400 transition"
+        >
+          Cancel
+        </Link>
+      </div>
     </form>
   </div>
 </template>