-- Courses belong to a Program (CEFR-style labels like A1..C2 will be configured separately).
CREATE TABLE courses (
    id BIGSERIAL PRIMARY KEY,
    program_id BIGINT NOT NULL REFERENCES programs (id) ON DELETE CASCADE,
    name VARCHAR(255) NOT NULL,
    description TEXT,
    thumbnail TEXT,
    created_at TIMESTAMPTZ NOT NULL DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMPTZ
);

CREATE INDEX idx_courses_program_id ON courses (program_id);
CREATE INDEX idx_courses_program_created ON courses (program_id, created_at DESC);