feat: arborescence interactive avec expand/collapse, breadcrumb et navigation par dossier

- API /api/local-workspace/tree: arbre récursif complet (support optionnel ?folder=ID)
- API /api/local-workspace/breadcrumb: fil d'Ariane parent pour un dossier
- Page /local-workspace: supporte ?folder=ID pour naviguer dans un dossier
- Sidebar: expand/collapse (▶/▼) sur les dossiers, clic dossier → /local-workspace?folder=ID
- CSS: styles chevron .tree-chevron, .tree-folder-link
- Alpine.js: expandedFolders, toggleTreeFolder, navigateToFolder

app/routers/dashboard.py

@@ -491,8 +491,11 @@ async def remove_member(request: Request, ws_id: int, user_id: int):
 # ═══════════ Local Workspace (file/folder CRUD) ═══════════
 
 @router.get("/local-workspace", response_class=HTMLResponse)
-async def local_workspace_page(request: Request):
-    """Local workspace page with file/folder tree."""
+async def local_workspace_page(request: Request, folder: int = None):
+    """Local workspace page with file/folder tree.
+    
+    If ?folder=ID is provided, shows that folder's contents with breadcrumb.
+    """
     from jinja2 import Environment, FileSystemLoader
     env = Environment(loader=FileSystemLoader("app/templates"))
     sidebar = _sidebar_data(request, [])
@@ -502,40 +505,108 @@ async def local_workspace_page(request: Request):
 
     ws = _get_active_workspace(request)
     ws_id = ws["id"] if ws else None
-    with get_conn() as conn:
-        rows = conn.execute(
-            "SELECT id, title FROM pages WHERE parent_id IS NULL AND workspace_id=? ORDER BY created_at DESC",
-            (ws_id,),
-        ).fetchall() if ws_id else []
-    items = [{"id": r["id"], "name": r["title"] or "Untitled", "type": "page"} for r in rows]
 
-    ctx = {**sidebar, "user": user, "workspace_name": sidebar.get("active_ws_name", "My Workspace"), "items": items}
+    # Build breadcrumb if navigating into a folder
+    breadcrumb = []
+    current_folder_id = folder
+    if folder and ws_id:
+        with get_conn() as conn:
+            breadcrumb = _build_breadcrumb(conn, folder)
+
+    ctx = {
+        **sidebar,
+        "user": user,
+        "workspace_name": sidebar.get("active_ws_name", "My Workspace"),
+        "current_folder_id": current_folder_id or 0,
+        "breadcrumb": breadcrumb,
+    }
     template = env.get_template("local_workspace.html")
     return template.render(**ctx)
 
 
 @router.get("/api/local-workspace/tree")
-async def local_workspace_tree(request: Request):
-    """Return the file/folder tree filtered by active workspace."""
+async def local_workspace_tree(request: Request, folder: int = None):
+    """Return the file/folder tree filtered by active workspace.
+    
+    If ?folder=ID is provided, returns only that folder's children.
+    Otherwise returns the full recursive tree from root.
+    """
     ws = _get_active_workspace(request)
     ws_id = ws["id"] if ws else None
+    if not ws_id:
+        return {"tree": [], "breadcrumb": []}
+
     with get_conn() as conn:
-        roots = conn.execute(
-            "SELECT id, title, parent_section FROM pages WHERE parent_id IS NULL AND workspace_id=? ORDER BY created_at DESC",
+        if folder:
+            # Show only this folder's children + build breadcrumb
+            children = _build_tree_children(conn, folder, ws_id)
+            breadcrumb = _build_breadcrumb(conn, folder)
+            return {"tree": children, "breadcrumb": breadcrumb, "current_folder": folder}
+        else:
+            # Full tree from root
+            roots = _build_tree_children(conn, None, ws_id)
+            return {"tree": roots, "breadcrumb": [], "current_folder": None}
+
+
+@router.get("/api/local-workspace/breadcrumb")
+async def local_workspace_breadcrumb(request: Request, folder: int):
+    """Return breadcrumb trail for a folder."""
+    with get_conn() as conn:
+        breadcrumb = _build_breadcrumb(conn, folder)
+    return {"breadcrumb": breadcrumb}
+
+
+def _build_tree_children(conn, parent_id: int | None, ws_id: int) -> list:
+    """Recursively build the tree of children for a node."""
+    if parent_id is None:
+        rows = conn.execute(
+            "SELECT id, title, parent_section FROM pages "
+            "WHERE parent_id IS NULL AND workspace_id=? ORDER BY created_at DESC",
             (ws_id,),
-        ).fetchall() if ws_id else []
+        ).fetchall()
+    else:
+        rows = conn.execute(
+            "SELECT id, title, parent_section FROM pages "
+            "WHERE parent_id=? AND workspace_id=? ORDER BY created_at DESC",
+            (parent_id, ws_id),
+        ).fetchall()
+    
     tree = []
-    for r in roots:
-        with get_conn() as conn:
-            children = conn.execute(
-                "SELECT id, title, parent_section FROM pages WHERE parent_id=? ORDER BY created_at", (r["id"],)
-            ).fetchall()
+    for r in rows:
         is_folder = r["parent_section"] == "Workspace"
-        rtype = "folder" if is_folder else "page"
-        item = {"id": r["id"], "name": r["title"] or "Untitled", "type": rtype,
-                "children": [{"id": c["id"], "name": c["title"] or "Untitled", "type": "page"} for c in children]}
-        tree.append(item)
-    return {"tree": tree}
+        children = _build_tree_children(conn, r["id"], ws_id)
+        tree.append({
+            "id": r["id"],
+            "name": r["title"] or "Untitled",
+            "type": "folder" if is_folder else "page",
+            "is_folder": is_folder,
+            "children": children,
+            "has_children": len(children) > 0,
+        })
+    return tree
+
+
+def _build_breadcrumb(conn, folder_id: int) -> list:
+    """Build breadcrumb trail from root to folder_id."""
+    breadcrumb = []
+    current = folder_id
+    seen = set()
+    while current and current not in seen:
+        seen.add(current)
+        row = conn.execute(
+            "SELECT id, title, parent_id, parent_section FROM pages WHERE id=?",
+            (current,),
+        ).fetchone()
+        if row:
+            breadcrumb.insert(0, {
+                "id": row["id"],
+                "name": row["title"] or "Untitled",
+                "is_folder": row["parent_section"] == "Workspace",
+            })
+            current = row["parent_id"]
+        else:
+            break
+    return breadcrumb
 
 
 @router.post("/api/local-workspace/items")