Add traditions field to user profile schema and API

[evanyerburgh]

Part of epic: #209

[Platform: App, Web, Studio]

Context

The user profile has no tradition field. POST /users/info and GET /users/info both exist but carry no tradition data. This is a schema addition to an existing endpoint — no new API path needed.

Why This Matters

The app needs to remember which traditions a user practices so it can filter content accordingly. Like language preference, this needs to be stored server-side — not locally — so it persists across devices and reinstalls.

Acceptance Criteria

• traditions field (list of strings) added to UserInfoRequest schema — accepted by POST /users/info
• traditions field added to UserInfoResponse schema — returned by GET /users/info
• An empty or missing traditions field is valid — treated as "All Traditions" (no filtering)
• Valid tradition IDs: theravada, pure_land, zen, tibetan, ambedkar, general — invalid values should be rejected

Flags

• ⚠️ Schema migration — existing user records will have no traditions value; treat null/missing as "All Traditions"