refactored auth for JWTs, completed TOTP/2FA implementation, added endpoints to change display name and password

backend/migrations/20260331222425_friends.sql

@@ -0,0 +1,13 @@
+-- Add migration script here
+CREATE TYPE status AS ENUM ('pending', 'accepted', 'blocked');
+
+CREATE TABLE relationships (
+    id          SERIAL PRIMARY KEY,
+    from_user   INTEGER NOT NULL REFERENCES users(id),
+    to_user     INTEGER NOT NULL REFERENCES users(id),
+    status      status NOT NULL DEFAULT 'pending',
+    created_at  TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    updated_at  TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    CONSTRAINT no_self_relationship CHECK (from_user != to_user),
+    CONSTRAINT unique_relationship UNIQUE (from_user, to_user)
+);