I am looking for a comprehensive list of Chasidic sefarim which deal with every one of the Moadim, in terms of Machshava/Hashkafa. One I know of so far which meets this criteria is Pri Tzaddik by Rav Tzadok HaKohen of Lublin, which deals exhaustively with every one of the holidays in the year, down to each Rosh Chodesh and minor holidays (such as Tu B'Shvat), from a Torah/Chasidic/Kabbalah perspective. I have also found the Sfas Emes, by the Gerrer Rebbe Yehuda Aryeh Leib Alter, to write extensively on the Moadim, although he doesn't include Rosh Chodesh or minor holidays.I focus my question on Chasidic sefarim because I have found them most likely to discuss these areas with the breadth I am looking for, but I am open to hearing of non-Chasidic sefarim which treat the Moadim similarly. Are there any other sefarim which take the cycle of the year so seriously in a Machshava fashion?
You can add the Shem MiShmuel by Rabbi Shmuel Bornsztain, the second Sochatchover Rebbe, to your list. Also, the Maharal MiPrague predates Hassidism but has been described as a forefather of Chassidus in terms of machshavic thought. (I believe he heavily influenced Rav Tzadok.) He has works related to many of the moadim including Gevurot Hashem on Pesach, Tiferes Yisrael on Shavuot, Netzach Yisrael on Tisha B'Av, Ner Mitzvah on Chanuka, and Ohr Chadash on Purim. (He had planned to write on the other Moadim as well but unfortunately never did.) Along those lines, you might also be interested in the Pachad Yitzchak of Rav Yitzchak Hutner, z"l.
This 17 volume set covers everything you're looking for. Each sefer covers both halacha, customs and Chassidic insights as explained by the Lubavitcher Rebbe. There are extensive footnotes to look up original sources.
This second set, Nitai Gavriel, is not specifically Chassidut. It is Halacha. But again, is excellent, informative and comprehensive. It is also heavily footnoted.
Nefesh Shimshon based on the lectures of Rabbi Shimshon Pinkus is one of those modern classics that has found a wide audience in this area.
The series does not cover all the moadim as of yet, see the list of works here