fix: FOREIGN KEY constraint failed on POST /api/workspaces

Bug: create_workspace in dashboard.py set uid=1 when session was
invalid, but user 1 might not exist in the users table, causing
sqlite3.IntegrityError: FOREIGN KEY constraint failed (HTTP 500).

Fix: ensure user row exists (INSERT OR IGNORE) before inserting
workspace with FK reference, matching the pattern in workspace.py.
Also: add name validation, use INSERT OR IGNORE for members.

app/routers/dashboard.py

@@ -659,18 +659,27 @@ async def create_workspace(request: Request):
     import json
     body = await request.json()
     name = body.get("name", "New Workspace").strip()
+    if not name:
+        return {"error": "Name required"}
     user = SessionManager.decode_session(request.cookies.get("flowdeck_session", ""))
     uid = user["id"] if user and user.get("id") else 1
     with get_conn() as conn:
+        # Ensure user exists (FK constraint)
+        uid_ok = conn.execute("SELECT id FROM users WHERE id=?", (uid,)).fetchone()
+        if not uid_ok:
+            conn.execute(
+                "INSERT OR IGNORE INTO users (id, login, full_name, is_admin) VALUES (?, ?, ?, 1)",
+                (uid, user.get("login", "admin") if user else "admin",
+                 user.get("full_name", "Admin") if user else "Admin"),
+            )
         cursor = conn.execute(
             "INSERT INTO workspaces (name, owner_id) VALUES (?, ?)",
             (name, uid),
         )
-        conn.commit()
         ws_id = cursor.lastrowid
         # Add owner as member
         conn.execute(
-            "INSERT INTO workspace_members (workspace_id, user_id, role) VALUES (?, ?, 'owner')",
+            "INSERT OR IGNORE INTO workspace_members (workspace_id, user_id, role) VALUES (?, ?, 'owner')",
             (ws_id, uid),
         )
         conn.commit()