Projects: shareable, registry-backed, container-mounted; drop ticket board

Rework projects from single-user leftovers into shareable endeavours.

- DB: move `projects` from the owner bucket to the registry (system.db,
  not encrypted); add `owner_user_id` + `slug` (drop free `path`); new
  `project_members(project_id, user_id, can_write)` mirroring
  `shared_folder_members`. Drop `project_tickets` entirely. Only user↔agent
  conversations stay encrypted (per-user DB) — each member keeps a private
  project chat. Registry home dissolves the cross-DB-FK problem.
- Filesystem/container: on disk `{WD}/projects/{owner_userid}/{slug}`,
  agent/container path `projects/{owner_username}/{slug}`. Two-segment routing
  in UserFs (ProjectMount + host_base_and_tail arm) and a second loop in
  build_user_fs; read-only members get a :ro mount. Reuse the shared-folder
  remount machinery (refresh_user_shared_folders -> refresh_user_mounts).
- Remove the ticket system: ProjectTicketManager, UserContext.tickets, its
  wiring, and the project_tickets references in scheduled_jobs/cron.
- API: repoint handlers to the registry pool + membership scoping. Sharing is
  self-service — owner or any write-member may add/remove members and set
  read/write; only the owner deletes; the owner cannot be removed. New
  POST/DELETE /api/projects/{id}/members[/{user_id}]. Seed `@fs_any allow
  projects/*`; build_runtime_run_context sets working_directory to the agent
  path and drops the host-path allow_fs_writes.
- Frontend: create form without the free path field, owner/read-write badges;
  the detail page becomes header + description + sharing panel + Open chat + a
  file-explorer placeholder (the future primary surface). i18n en/it/fr.

web/i18n/it.js

@@ -208,14 +208,15 @@ export default {
   'projects.action.edit':           'Modifica',
   'projects.action.delete':         'Elimina',
   'projects.card.updated':          'Aggiornato',
-  'projects.confirm.delete':        'Eliminare il progetto "{name}"?\nTutti i ticket verranno eliminati.',
+  'projects.confirm.delete':        'Eliminare il progetto "{name}"? Verrà rimosso per tutti coloro con cui è condiviso.',
+  'projects.badge.owned':           'Tuo',
+  'projects.badge.shared_by':       'Condiviso da {name}',
+  'projects.badge.readonly':        'Sola lettura',
 
   'projects.modal.title_edit':      'Modifica progetto',
   'projects.modal.title_new':       'Nuovo progetto',
   'projects.modal.name':            'Nome',
   'projects.modal.name_ph':         'Mio progetto',
-  'projects.modal.path':            'Percorso',
-  'projects.modal.path_ph':         '/percorso/del/progetto',
   'projects.modal.desc':            'Descrizione',
   'projects.modal.desc_ph':         'Di cosa tratta questo progetto',
   'projects.modal.cancel':          'Annulla',
@@ -223,36 +224,22 @@ export default {
   'projects.modal.save':            'Salva',
   'projects.modal.create':          'Crea',
 
-  // ── Project board ───────────────────────────────────────────────────────────
+  // ── Condivisione progetto ───────────────────────────────────────────────────
+  'projects.share.title':           'Condivisione',
+  'projects.share.owner':           'proprietario',
+  'projects.share.choose_user':     'Scegli una persona…',
+  'projects.share.add':             'Aggiungi',
+  'projects.share.all_added':       'Tutti hanno già accesso.',
+  'projects.share.remove':          'Rimuovi',
+  'projects.share.access.read':     'Lettura',
+  'projects.share.access.write':    'Scrittura',
+  'projects.share.access.readonly': 'Sola lettura',
+  'projects.share.access.readwrite':'Lettura e scrittura',
+  'projects.files.placeholder':     'Qui vivono i file del progetto. Apri la chat per lavorare in questa cartella — un file explorer è in arrivo.',
+
+  // ── Dettaglio progetto ──────────────────────────────────────────────────────
   'project_board.back':               'Progetti',
   'project_board.open_chat':          'Apri chat',
-  'project_board.new_ticket':         'Nuovo ticket',
-  'project_board.tab.tickets':        'Ticket',
-  'project_board.section.running':    'In esecuzione',
-  'project_board.section.running_empty': 'Nessun ticket in esecuzione',
-  'project_board.section.todo':       'Da fare',
-  'project_board.section.todo_empty': 'Nessun ticket da fare',
-  'project_board.section.completed':  'Completati',
-  'project_board.section.completed_empty': 'Nessun ticket completato',
-  'project_board.ticket.start':       'Avvia',
-  'project_board.ticket.running':     'In esecuzione…',
-  'project_board.ticket.reset':       'Reimposta',
-  'project_board.ticket.result':      'Risultato',
-  'project_board.ticket.error':       'Errore',
-  'project_board.ticket.no_output':   '(nessun output)',
-  'project_board.ticket.no_error':    '(nessun errore)',
-  'project_board.modal.title':        'Nuovo ticket',
-  'project_board.modal.title_label':  'Titolo',
-  'project_board.modal.title_ph':     'Cosa bisogna fare',
-  'project_board.modal.desc_label':   'Descrizione / Prompt',
-  'project_board.modal.desc_ph':      'Istruzioni dettagliate per l\'agente…',
-  'project_board.modal.agent':        'Agente',
-  'project_board.modal.security_group':'Gruppo di sicurezza',
-  'project_board.modal.inherit':      '— eredita dal progetto —',
-  'project_board.modal.cancel':       'Annulla',
-  'project_board.modal.saving':       'Salvataggio…',
-  'project_board.modal.create':       'Crea',
-  'project_board.confirm.delete':     'Eliminare il ticket "{title}"?',
 
   // ── Richieste ──────────────────────────────────────────────────────────────
   'inbox.empty':         'Nessuna richiesta in attesa',