feat: onglet de navigation avec facettes, tris et retour Home complet #158

- clic sur un repertoire de l'arbre (modes focus vault et All) ouvre un onglet de navigation dedie qui coexiste avec les onglets de fichiers ouverts
- vue: sous-repertoires cliquables, facettes Vaults/Tags/Extensions (meme mecanisme que la recherche), tris Pertinence/Date, bouton Sauver; tags indexes exposes par GET /api/vault/{v}/files
- BUG-100: showWelcome re-injecte la section Raccourcis & Astuces et goHome efface la recherche globale + le filtre de la sidebar

backend/schemas.py

@@ -863,6 +863,7 @@ class VaultFileEntry(BaseModel):
     modified_iso: str | None = None
     extension: str = ""
     rel_dir: str | None = None
+    tags: list[str] = Field(default_factory=list, description="Tags de l'index (#158)")
 
 
 class VaultFilesResponse(BaseModel):

backend/services/vaults.py

@@ -102,6 +102,29 @@ def browse_directory(vault_name: str, path: str = "") -> dict[str, Any]:
     return {"vault": vault_name, "path": path, "items": items}
 
 
+def _indexed_tags(vault_name: str, rel_path: str) -> list[str]:
+    """Tags of a file as stored in the search index (#158).
+
+    Empty list when the file is not indexed yet (binary formats, index still
+    building) — the listing itself comes from the filesystem, tags are a
+    decoration used by the navigation page facets/filters.
+
+    Args:
+        vault_name: Vault name.
+        rel_path: Path of the file relative to the vault root (``/`` separated).
+
+    Returns:
+        The file's tags, or an empty list when unknown.
+    """
+    try:
+        from backend.search import get_inverted_index
+
+        info = get_inverted_index().doc_info.get(f"{vault_name}::{rel_path}")
+    except Exception:
+        return []
+    return list((info or {}).get("tags") or [])
+
+
 def list_all_files(
     vault_name: str,
     dir: str = "",
@@ -189,6 +212,7 @@ def list_all_files(
                 "modified": stat.st_mtime,
                 "modified_iso": datetime.fromtimestamp(stat.st_mtime, tz=timezone.utc).isoformat(),
                 "extension": ext.lstrip(".") if ext else "",
+                "tags": _indexed_tags(vault_name, rel_path),
             }
             if rel_to_dir and rel_to_dir != ".":
                 file_entry["rel_dir"] = rel_to_dir