feat: add public read-only sharing for computers

Adds the ability for an owner to share a computer build via a public,
unauthenticated link, inspired by a feature request from the original
pcbuilder repo (no such feature actually existed there — implemented
from scratch here).

- New columns on computers: share_token (unique, nullable), share_enabled,
  share_show_sell_price, share_show_cost
- computer_share_service.ts: generates a non-guessable share token
  (crypto.randomBytes, base64url), enables/disables sharing, and supports
  rotating the token to invalidate previously distributed links
- ComputerShareController (authenticated, owner-scoped like the rest of
  the app): PUT /computers/:id/share to update settings, POST
  /computers/:id/share/rotate to rotate the token
- PublicComputerController + GET /share/:token (outside any auth/guest
  group, reachable anonymously): resolves only computers with
  share_enabled = true, 404 otherwise
- ComputerPublicTransformer: dedicated read-only projection that never
  leaks userId, and only includes sellPrice/cost when the owner opted in
  via share_show_sell_price / share_show_cost — everything else (title,
  scores, state, components, pictures) is always visible on a shared link
- ComputerShareModal.vue: owner-facing UI (toggle sharing, choose which
  prices to expose, copy the public link, revoke/rotate it) wired into
  computers/show.vue via a new 'Share' button
- share/show.vue: public page rendered with EmptyLayout (no authenticated
  header/sidebar)
- Boolean columns use a  cast since MySQL returns tinyint(1),
  not native booleans, through Lucid
- 6 new functional tests covering: enabling sharing, price visibility
  toggles, disabling sharing revokes the link, cross-user protection on
  the share settings endpoint (404), token rotation invalidating the old
  link, and anonymous access to a shared computer

start/routes.ts

@@ -11,9 +11,11 @@ import { middleware } from '#start/kernel'
 import { controllers } from '#generated/controllers'
 import router from '@adonisjs/core/services/router'
 
-router.get('/', async ({ response }) => {
-  return response.redirect('/auth/login')
-}).as('home')
+router
+  .get('/', async ({ response }) => {
+    return response.redirect('/auth/login')
+  })
+  .as('home')
 
 router
   .group(() => {
@@ -42,10 +44,16 @@ router
     router.get('/:id/edit', [controllers.Computers, 'edit']).as('computers.edit')
     router.put('/:id', [controllers.Computers, 'update']).as('computers.update')
     router.delete('/:id', [controllers.Computers, 'destroy']).as('computers.destroy')
+    router.put('/:id/share', [controllers.ComputerShare, 'update']).as('computers.share.update')
+    router
+      .post('/:id/share/rotate', [controllers.ComputerShare, 'rotate'])
+      .as('computers.share.rotate')
   })
   .prefix('/computers')
   .use(middleware.auth())
 
+router.get('/share/:token', [controllers.PublicComputer, 'show']).as('share.show')
+
 router
   .group(() => {
     router.get('/', [controllers.Components, 'index']).as('components.index')