I want to give you a virtual hug as I could had written the exact same things for me. I struggle with the same stuff and now being close to my 40s it is exhausting. I got diagnosed with ADHD before almost 5 years but as I look deeper into I tend to believe it must be more like a childhood trauma result than just genetics. Lookup C-PTSD and the overlapping symptoms are way too much for this would be just a coincidence. But every step towards a better situation is a good step.

My browser uses the same algorithm, so the text I entered is “2gtth5” now. The server looks up my hashed password

This is not correct. Your browser will submit “shark” and then the backend server will do whatever hashing is required and after that it will compare the hashes. If hashing was happening in the browser that would mean that an attacker would be be able to attack by using just the hashes of the passwords, not the passwords themselves. Also in such case, the browser would had been responsible to do the required salting which in turn would make it pointless as it would had been known.