X-related is not required to come before or after what it modifies. It is all things which is idiomatic, and makes you question the word position.
The Biblical all things to all men may explain its popularity, or to a lesser extent, all things must pass. Regardless of origin, however, all things remains a very frequent collocation, found in such expressions as all things being equal or of all things! The flagship news program on National Public Radio (US) is All Things Considered, and for an extensive review of American stereotypes of Scotland, there is the old Saturday Night Live sketch about a store named All Things Scottish (and Pizza).
To insert an adjective before things violates no grammatical rule. One could conceivably say We need more purple things for Mardis Gras decorations, or What are all the round things on the left of the banner? In a CV, however, I would avoid vague words like things in favor of specific terminology.
Software engineer with a passion for all things user-related.
Software engineer with a passion for user-related design and development.
(The term would indeed be user-related, as with user access, user error, and so on.)
All things is somewhat more grandiose than everything, and sometimes they can substitute for one another. One could plausibly say I'm interested in everything Turkish and I'm interested in all things Turkish in conversation. On the other hand, You're all things I want in a woman sounds stilted, and I'd like a pizza with all things on it will get you a quizzical look. And no pizza.