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/fr.js

@@ -184,14 +184,15 @@ export default {
   'projects.action.edit':           'Modifier',
   'projects.action.delete':         'Supprimer',
   'projects.card.updated':          'Mis à jour',
-  'projects.confirm.delete':        'Supprimer le projet "{name}" ?\nTous les tickets seront également supprimés.',
+  'projects.confirm.delete':        'Supprimer le projet "{name}" ? Il sera retiré pour toutes les personnes avec qui il est partagé.',
+  'projects.badge.owned':           'Le vôtre',
+  'projects.badge.shared_by':       'Partagé par {name}',
+  'projects.badge.readonly':        'Lecture seule',
 
   'projects.modal.title_edit':      'Modifier le projet',
   'projects.modal.title_new':       'Nouveau projet',
   'projects.modal.name':            'Nom',
   'projects.modal.name_ph':         'Mon projet',
-  'projects.modal.path':            'Chemin',
-  'projects.modal.path_ph':         '/chemin/vers/le/projet',
   'projects.modal.desc':            'Description',
   'projects.modal.desc_ph':         'À propos de ce projet',
   'projects.modal.cancel':          'Annuler',
@@ -199,36 +200,22 @@ export default {
   'projects.modal.save':            'Enregistrer',
   'projects.modal.create':          'Créer',
 
-  // ── Project board ───────────────────────────────────────────────────────────
+  // ── Partage de projet ───────────────────────────────────────────────────────
+  'projects.share.title':           'Partage',
+  'projects.share.owner':           'propriétaire',
+  'projects.share.choose_user':     'Choisir une personne…',
+  'projects.share.add':             'Ajouter',
+  'projects.share.all_added':       'Tout le monde a déjà accès.',
+  'projects.share.remove':          'Retirer',
+  'projects.share.access.read':     'Lecture',
+  'projects.share.access.write':    'Écriture',
+  'projects.share.access.readonly': 'Lecture seule',
+  'projects.share.access.readwrite':'Lecture et écriture',
+  'projects.files.placeholder':     'Les fichiers du projet vivent ici. Ouvrez la discussion pour travailler dans ce dossier — un explorateur de fichiers arrive bientôt.',
+
+  // ── Détail du projet ────────────────────────────────────────────────────────
   'project_board.back':               'Projets',
   'project_board.open_chat':          'Ouvrir la discussion',
-  'project_board.new_ticket':         'Nouveau ticket',
-  'project_board.tab.tickets':        'Tickets',
-  'project_board.section.running':    'En cours',
-  'project_board.section.running_empty': 'Aucun ticket en cours',
-  'project_board.section.todo':       'À faire',
-  'project_board.section.todo_empty': 'Aucun ticket à faire',
-  'project_board.section.completed':  'Terminé',
-  'project_board.section.completed_empty': 'Aucun ticket terminé',
-  'project_board.ticket.start':       'Démarrer',
-  'project_board.ticket.running':     'En cours…',
-  'project_board.ticket.reset':       'Réinitialiser',
-  'project_board.ticket.result':      'Résultat',
-  'project_board.ticket.error':       'Erreur',
-  'project_board.ticket.no_output':   '(aucune sortie)',
-  'project_board.ticket.no_error':    '(aucun message d\'erreur)',
-  'project_board.modal.title':        'Nouveau ticket',
-  'project_board.modal.title_label':  'Titre',
-  'project_board.modal.title_ph':     'Ce qui doit être fait',
-  'project_board.modal.desc_label':   'Description / Prompt',
-  'project_board.modal.desc_ph':      'Instructions détaillées pour l\'agent…',
-  'project_board.modal.agent':        'Agent',
-  'project_board.modal.security_group':'Groupe de sécurité',
-  'project_board.modal.inherit':      '— hériter du projet —',
-  'project_board.modal.cancel':       'Annuler',
-  'project_board.modal.saving':       'Enregistrement…',
-  'project_board.modal.create':       'Créer',
-  'project_board.confirm.delete':     'Supprimer le ticket "{title}" ?',
 
   // ── Session detail ──────────────────────────────────────────────────────────
   'session.back':             'Retour',