projects: file explorer, ws improvements, i18n, and fs routing

Add project-files component with tree navigation. Extend UserFs with
shared-folder resolution. Wire API routes for file browsing. Improve
WS session lifecycle and project-board layout. Add i18n keys for
projects and inbox across all locales.

web/components/projects/index.js

@@ -8,6 +8,7 @@ export class ProjectsPage extends LightElement {
     _open:      { state: true },
     _view:      { state: true },
     _projectId: { state: true },
+    _tab:       { state: true },
   };
 
   constructor() {
@@ -15,6 +16,7 @@ export class ProjectsPage extends LightElement {
     this._open      = false;
     this._view      = 'list';
     this._projectId = null;
+    this._tab       = 'files';
   }
 
   connectedCallback() {
@@ -24,9 +26,25 @@ export class ProjectsPage extends LightElement {
       this._open = open;
       this.style.display = open ? 'flex' : 'none';
       if (open) {
-        const { view, id } = this._parseHash();
+        const { view, id, tab } = this._parseHash();
         this._view      = view;
         this._projectId = id;
+        this._tab       = tab;
+        this._loadCurrent();
+      }
+    });
+    window.addEventListener('hashchange', () => {
+      // Back/forward (or manual edit) between board tabs: same project → just
+      // switch the tab, no reload; anything else → re-sync from the hash.
+      if (!this._open || !location.hash.startsWith('#projects')) return;
+      const { view, id, tab } = this._parseHash();
+      if (view === 'board' && this._view === 'board' && id === this._projectId) {
+        this._tab = tab;
+        this.querySelector('project-board-section')?.setTab(tab);
+      } else {
+        this._view      = view;
+        this._projectId = id;
+        this._tab       = tab;
         this._loadCurrent();
       }
     });
@@ -40,9 +58,10 @@ export class ProjectsPage extends LightElement {
   _parseHash() {
     const parts = location.hash.slice(1).split('/');
     if (parts[0] === 'projects' && parts[1] && /^\d+$/.test(parts[1])) {
-      return { view: 'board', id: parseInt(parts[1], 10) };
+      const tab = parts[2] === 'sharing' ? 'sharing' : 'files';
+      return { view: 'board', id: parseInt(parts[1], 10), tab };
     }
-    return { view: 'list', id: null };
+    return { view: 'list', id: null, tab: 'files' };
   }
 
   _loadCurrent() {
@@ -50,7 +69,7 @@ export class ProjectsPage extends LightElement {
       if (this._view === 'list') {
         this.querySelector('project-list-section')?.load();
       } else {
-        this.querySelector('project-board-section')?.load(this._projectId);
+        this.querySelector('project-board-section')?.load(this._projectId, this._tab);
       }
     });
   }
@@ -58,9 +77,10 @@ export class ProjectsPage extends LightElement {
   _navigateToBoard(id) {
     this._view      = 'board';
     this._projectId = id;
+    this._tab       = 'files';
     history.pushState({ page: 'projects', id }, '', `#projects/${id}`);
     this.updateComplete.then(() => {
-      this.querySelector('project-board-section')?.load(id);
+      this.querySelector('project-board-section')?.load(id, 'files');
     });
   }
 
@@ -73,6 +93,12 @@ export class ProjectsPage extends LightElement {
     });
   }
 
+  _onTabChange(tab) {
+    this._tab = tab;
+    const hash = tab === 'sharing' ? `#projects/${this._projectId}/sharing` : `#projects/${this._projectId}`;
+    history.pushState({ page: 'projects', id: this._projectId }, '', hash);
+  }
+
   render() {
     if (!this._open) return nothing;
     return html`
@@ -83,6 +109,7 @@ export class ProjectsPage extends LightElement {
       ` : html`
         <project-board-section
           @project-back=${() => this._navigateToList()}
+          @project-tab-change=${e => this._onTabChange(e.detail.tab)}
         ></project-board-section>
       `}
     `;