feat: sous-pages — parent_id, sidebar hiérarchique, bouton +New sub-page

- DB: parent_id dans table pages (ALTER TABLE migration auto)
- Sidebar: pages parent_id IS NULL affichées, sous-pages indentées en dessous
- API: create_page accepte parent_id (0 = racine)
- JS: newSubPage extrait page ID et passe parent_id
- page_editor: liste les sous-pages + bouton '+ New sub-page'

app/routers/board.py

@@ -139,7 +139,7 @@ def _sidebar_data(request: Request, owner: str = "", repo: str = "") -> dict:
     # Load pages for this project workspace
     with get_conn() as conn:
         pages = conn.execute(
-            "SELECT id, title, updated_at FROM pages WHERE workspace=? ORDER BY updated_at DESC LIMIT 10",
+            "SELECT id, title, parent_id, updated_at FROM pages WHERE workspace=? AND parent_id IS NULL ORDER BY updated_at DESC LIMIT 10",
             (ws_key,),
         ).fetchall()
         for p in pages:
@@ -147,6 +147,16 @@ def _sidebar_data(request: Request, owner: str = "", repo: str = "") -> dict:
                 "id": f"page/{p['id']}", "name": p["title"], "icon": "📄",
                 "url": f"/pages/{p['id']}", "active": False, "indent": 0,
             })
+            # Load sub-pages
+            subs = conn.execute(
+                "SELECT id, title FROM pages WHERE parent_id=? ORDER BY updated_at DESC",
+                (p["id"],),
+            ).fetchall()
+            for sp in subs:
+                recent.append({
+                    "id": f"page/{sp['id']}", "name": sp["title"], "icon": "·",
+                    "url": f"/pages/{sp['id']}", "active": False, "indent": 1,
+                })
     return {"workspace_name": ws_name, "workspace_initial": ws_name[0].upper() if ws_name else "B",
             "current_page": repo or "Dashboard", "last_edited": "now",
             "recent_pages": recent, "private_pages": [r for r in recent if r.get("active") or r["id"].startswith("page/")],
@@ -439,18 +449,19 @@ async def extract_ai_keywords(owner: str, repo: str):
 @router.post("/api/pages")
 async def create_page(request: Request, title: str = Query(default="New page"),
                        section: str = Query(default="Private"),
-                       project: str = Query(default="")):
-    """Create a new Markdown page in the given project workspace."""
+                       project: str = Query(default=""),
+                       parent_id: int = Query(default=0)):
+    """Create a new Markdown page, optionally as a sub-page."""
     user = SessionManager.decode_session(request.cookies.get("flowdeck_session", ""))
     ws_key = project if project else (user.get("login", "Bruno") if user else "Bruno")
     with get_conn() as conn:
         cur = conn.execute(
-            "INSERT INTO pages (workspace, title, parent_section) VALUES (?,?,?)",
-            (ws_key, title, section),
+            "INSERT INTO pages (workspace, title, parent_section, parent_id) VALUES (?,?,?,?)",
+            (ws_key, title, section, parent_id if parent_id > 0 else None),
         )
         conn.commit()
         page_id = cur.lastrowid
-    return {"status": "ok", "id": page_id, "title": title, "workspace": ws_key}
+    return {"status": "ok", "id": page_id, "title": title, "workspace": ws_key, "parent_id": parent_id}
 
 
 @router.get("/api/pages/{page_id}")

app/routers/dashboard.py

@@ -71,7 +71,13 @@ async def view_page_root(request: Request, page_id: int):
     parts = ws.split("/") if "/" in ws else ["", ""]
     owner, repo = parts[0], parts[1] if len(parts) > 1 else ""
     sidebar = board_sidebar(request, owner, repo)
-    ctx = {**sidebar, "page": page}
+    # Load sub-pages
+    with get_conn() as conn:
+        subs = conn.execute(
+            "SELECT id, title FROM pages WHERE parent_id=? ORDER BY updated_at DESC",
+            (page_id,),
+        ).fetchall()
+    ctx = {**sidebar, "page": page, "sub_pages": [dict(s) for s in subs]}
     template = env.get_template("page_editor.html")
     return template.render(**ctx)