Add PlanningSessionFiles, PlanningSessionStartContext/ResumeContext DTOs,
PlanningSessionManager.StartAsync (file scaffolding + status transition),
and integration tests. Also fix migration discovery by adding [DbContext]
attribute to all migration classes and switch DbFixture to EnsureCreated.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Delete SqliteConnectionFactory, SchemaInitializer, and schema.sql.
Fix ValueConverter lambdas in entity configurations (no throw-expressions
in expression trees). Add IDesignTimeDbContextFactory for dotnet-ef tooling.
Generate InitialCreate migration with seed data for agent/manual tags.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
