feat: v6.1.0 granular permissions (page/collection/property ACL + groups + audit)

- Migration 18: 6 tables + 3 colonnes permission_type + indexes
- PermissionManager: heritage page->collection->workspace, least privilege, groups, cache 60s
- API /api/v2: pages/collections/properties/groups/users/audit (401/403/404/400)
- Guards board.py + collections.py (404/403, admin/owner bypass)
- Tests 21/21 (inherit/restricted/private, grant, revoke, batch, group, audit)
- Docs + ROADMAP + CHANGELOG + VERSION 6.1.0

CHANGELOG.md

@@ -1,5 +1,46 @@
 # Changelog - FlowDeck
 
+## v6.1.0 (2026-09-19) — Granular Permissions : page / collection / property ACL + groupes + audit
+
+> Permissions fines héritables : chaque page / database / propriété peut être restreinte à des utilisateurs ou groupes explicites. L'héritage suit la chaîne page → collection → workspace (moindre privilège), avec bypass owner/admin et audit complet.
+
+### Base de données (migration 18)
+
+- Tables `user_groups` (workspace-scoped, UNIQUE(name)), `group_members` (N-ary), `page_permissions`, `collection_permissions`, `property_permissions` (user_id XOR group_id, CHECK, UNIQUE), `permission_audit_log`.
+- Colonnes `pages.permission_type`, `collections.permission_type`, `collection_pages.permission_type` (`inherit|restricted|private`, défaut `inherit`).
+- Index `idx_pp_page`, `idx_pp_user`, `idx_cp_collection`, `idx_propp_prop`, `idx_perm_audit_res`, `idx_gm_*`.
+
+### PermissionManager (`app/services/permission_manager.py`)
+
+- Résolution héritage + moindre privilège : grant explicite sur page > grant collection > rôle workspace ; `restricted`/`private` sans grant → 404.
+- Méthodes page : `get_page_permission()`, `can_view/edit/comment/manag` ; collection : `get_collection_permission()`, `can_view/edit/manag` ; propriété : `can_view/edit_property()`, `get_visible_properties()`.
+- Groupes : `create_group()`, `add/remove_user_from_group()`, `get_groups_for_workspace()`, `get_group_members()`, `is_workspace_admin()`, `user_group_ids()`.
+- Helpers : `_explicit_grant_role()` (best rank user+groups), `_collection_role()`, `_property_*`, `_owns_workspace()`, `_is_admin()`.
+- Cache 60 s (`_cached()`) + `invalidate()` appelé après chaque grant/revoke/type_change.
+- `log_permission_change()` (audit, never-throw).
+
+### API (`app/routers/permissions.py` — `prefix /api/v2`)
+
+- Pages : `GET /pages/{id}/permissions` (grants + mine + type + can_manage), `GET /pages/{id}/permissions/mine`, `POST /pages/{id}/permissions` (user_id|group_id + role viewer/commenter/editor/owner), `POST /pages/{id}/permissions/batch`, `DELETE /pages/{id}/permissions/{perm_id}`, `POST /pages/{id}/permission-type`.
+- Collections : `GET /collections/{id}/permissions`, `POST /collections/{id}/permissions`, `DELETE /collections/{id}/permissions/{perm_id}`, `POST /collections/{id}/permission-type`, `GET /collections/{id}/properties/visible` (split visible/hidden).
+- Properties : `GET /collections/{cid}/properties/{pid}/permissions`, `POST …/permissions` (role viewer|editor), `DELETE …/permissions/{perm_id}` (extra_cols collection_id).
+- Groupes : `GET /groups?workspace_id`, `POST /groups`, `PUT /groups/{id}`, `DELETE /groups/{id}`, `GET/POST /groups/{id}/members`, `DELETE /groups/{id}/members/{uid}` (workspace owner/admin only).
+- Access pickers + audit : `GET /users?workspace_id&q`, `GET /audit/permissions?limit` (owner/admin, 500 max).
+- Validation : 401 sans session, 403 sans can_manage, 400 rôle invalide / cible manquante, 404 user/group/property inconnu.
+
+### Guards existants
+
+- `board.py` : `GET /board/api/pages/{id}` (404 si !can_view_page), `PUT /board/api/pages/{id}` (404 si non-view, 403 si viewer/commenter, 423 si locked reste prioritaire).
+- `collections.py` : `DELETE /db/api/{id}` (404 si !can_view_collection, 403 si !can_manage), `GET /db/pages/{id}/api` (404), `PUT/DELETE /db/pages/{id}/api` (403), `GET /db/{id}/properties/api` filtré par visible, `_require_view/_require_edit` helpers avec `_session_user()` (pas de fallback admin sur null session).
+
+### UI (backend-ready)
+
+- Endpoints prêts pour panneau Permissions de l'éditeur (icône 🔒), panneau collection, masquage colonnes via `visible`/`hidden`, et gestion des groupes en Settings. Les grants sont consommés par `can_view_property` / `get_visible_properties` côté vues.
+
+### Tests
+
+- `tests/test_v60_granular_permissions.py` — **21 tests** : inherit allow + edit 403, restricted hidden (owner 200 / member 404), grant viewer unlock + viewer cannot edit, editor can edit but not manage, revoke 404, private + admin override, mine + batch, permission-type via API, restricted collection hidden (API 404 + HTML 302), collection viewer 403 create/delete, owner delete, collection editor create pages, property visibility, property hidden, property grant 403, group grant inherits + listing shows group, group removal revokes, groups listing/members + non-owner 403, audit log (grant+type_change, member 403), endpoints 401, validation 404/400. Suite 21/21 verte.
+
 ## v6.0.0 (2026-09-18) — PWA : Progressive Web App, offline support
 
 > FlowDeck devient une PWA installable et utilisable hors ligne : le shell est