Is he who attempted suicide and died affected by his injury a year later, repentant and remorseful, considered to have died by suicide?

A person who repents from attempting suicide is not considered a suicide. Repentance is valid for all sins as long as the servant has not witnessed death. Allah forgives all sins for those who repent, and no sin is too great for His forgiveness for one who repents sincerely, as Allah Almighty said: "Say, 'O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allah. Indeed, Allah forgives all sins. Indeed, it is He who is the Forgiving, the Merciful.'" And the one who repents from a sin is like one who has no sin, and he will not be punished for it in this world or in the Hereafter.