Plan: pin NuGet package versions to 9.* for net9.0 compat

docs/superpowers/plans/2026-08-15-supabase-todo-app.md

@@ -293,11 +293,11 @@ Confirm `git status` does NOT list `backend/appsettings.Development.json`.
 
 ```bash
 cd backend
-dotnet add package Microsoft.EntityFrameworkCore
-dotnet add package Npgsql.EntityFrameworkCore.PostgreSQL
+dotnet add package Microsoft.EntityFrameworkCore --version 9.*
+dotnet add package Npgsql.EntityFrameworkCore.PostgreSQL --version 9.*
 ```
 
-No `--version` — the CLI resolves the latest stable compatible with the SDK (9.x on this project).
+`--version 9.*` pins to the 9.x major line. Without it, `dotnet add package` picks the absolute-latest stable (e.g. 10.x once released) which will not resolve against `net9.0` — `NU1202` error.
 
 - [ ] **Step 2: Create the `Todo` entity**
 
@@ -409,9 +409,11 @@ git commit -m "Add EF Core, Npgsql, Todo entity, and AppDbContext"
 
 ```bash
 cd backend
-dotnet add package Microsoft.AspNetCore.Authentication.JwtBearer
+dotnet add package Microsoft.AspNetCore.Authentication.JwtBearer --version 9.*
 ```
 
+Same reason as Task 4: pin the major to avoid picking a version incompatible with `net9.0`.
+
 - [ ] **Step 2: Wire authentication in `Program.cs`**
 
 Open `backend/Program.cs`. Add these two `using` directives at the top (below the existing `using` lines):