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.

crates/skald-core/src/skald/bundles.rs

@@ -30,8 +30,6 @@ use crate::location::LocationManager;
 use crate::mcp::McpManager;
 use crate::memory::MemoryManager;
 use crate::plugin::PluginManager;
-use crate::projects::tickets::ProjectTicketManager;
-use crate::projects::ProjectManager;
 use crate::provider::ProviderRegistry;
 use crate::run_context::RunContextManager;
 use crate::secrets::SecretsStore;
@@ -174,12 +172,10 @@ impl Integrations {
     }
 }
 
-// ── Tasks: cron + projects/tickets ──────────────────────────────────────────
+// ── Tasks: cron ──────────────────────────────────────────────────────────────
 
 pub(super) struct Tasks {
-    pub(super) cron:           Arc<TaskManager>,
-    pub(super) projects:       Arc<ProjectManager>,
-    pub(super) ticket_manager: Arc<ProjectTicketManager>,
+    pub(super) cron: Arc<TaskManager>,
 }
 
 impl Tasks {
@@ -193,11 +189,7 @@ impl Tasks {
         });
         let cron = TaskManager::new(Arc::clone(&rt.db), cron_tz, Arc::clone(&rt.system_bus));
 
-        let ticket_manager = ProjectTicketManager::new(Arc::clone(&rt.db));
-        let projects       = Arc::new(ProjectManager::new(Arc::clone(&rt.db)));
-        info!("project manager ready");
-
-        Tasks { cron, projects, ticket_manager }
+        Tasks { cron }
     }
 }
 
@@ -353,6 +345,7 @@ impl Conversation {
             "skald-ownerless",
             std::path::PathBuf::from("/root"),
             Vec::new(),
+            Vec::new(),
         ));
 
         let manager = Arc::new(ChatSessionManager::new(