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/user_context.rs

@@ -51,7 +51,6 @@ use crate::inbox::Inbox;
 use crate::llm::LlmManager;
 use crate::mcp::{McpManager, McpProvider, UserMcpView};
 use crate::memory::MemoryManager;
-use crate::projects::tickets::ProjectTicketManager;
 use crate::run_context::RunContextManager;
 use crate::session::handler::{DEFAULT_MAX_PARALLEL_SUBAGENTS, DEFAULT_MAX_TOOL_ROUNDS};
 use crate::session::manager::ChatSessionManager;
@@ -74,7 +73,6 @@ pub struct UserContext {
     pub sessions:      Arc<ChatSessionManager>,
     pub chat_hub:      Arc<ChatHub>,
     pub cron:          Arc<TaskManager>,
-    pub tickets:       Arc<ProjectTicketManager>,
     pub approval:      Arc<ApprovalManager>,
     pub clarification: Arc<ClarificationManager>,
     pub elicitation:   Arc<ElicitationManager>,
@@ -291,29 +289,12 @@ impl UserContextFactory {
         cron.set_self_arc(Arc::clone(&cron));
         chat_hub.set_task_mgr(Arc::clone(&cron));
 
-        // Per-user ticket manager — wired to the per-user TaskManager so
-        // `start_ticket` spawns jobs in the user's own pool.
-        let tickets = ProjectTicketManager::new(Arc::clone(&pool));
-        tickets.set_task_manager(Arc::clone(&cron));
-
         // Per-user cron loop. `start()` observes the shutdown token, so it stops on
         // shutdown; adopting it lets the supervisor also join it. The name is leaked
         // to satisfy the `&'static str` label — bounded by the (small) user count.
         let name: &'static str = Box::leak(format!("cron:{user_id}").into_boxed_str());
         self.supervisor.adopt(name, Arc::clone(&cron).start(self.shutdown_token.clone()));
 
-        // Per-user ticket-listener: reacts to JobCompleted events for this user's
-        // tickets. All users' listeners receive the event (global system bus); only
-        // the one that owns the ticket does the UPDATE — others no-op on 0 rows.
-        let tname: &'static str = Box::leak(format!("tickets:{user_id}").into_boxed_str());
-        self.supervisor.adopt_one(
-            tname,
-            Arc::clone(&tickets).start_listener(
-                Arc::clone(&self.system_bus),
-                self.shutdown_token.clone(),
-            ),
-        );
-
         Ok(Arc::new(UserContext {
             user_id: user_id.to_string(),
             pool,
@@ -322,7 +303,6 @@ impl UserContextFactory {
             sessions: manager,
             chat_hub,
             cron,
-            tickets,
             approval,
             clarification,
             elicitation,