chore: studymap.config bounds/cities contradict the now-global dataset (two sources of truth)

[shauryagangrade]

Problem

studymap.config.ts:36-43 hardcodes:

• bounds to the Mumbai region (lat ~18-20, lng ~72-73)
• cities to the original 3 MMR cities

…while the dataset has grown to hundreds of city slugs spanning Vancouver → Cairo → Jakarta. The comment claims bounds are "used for data validation and map fitting", but scripts/validate-places.mjs actually reads its coordinate limits from data/places.schema.json (-90..90) — so the config's bounds are dead, wrong, and misleading to anyone forking the repo.

Suggested fix

Decide what each setting means and make it true:

1. Either widen/remove bounds, or scope it to what actually consumes it
2. Derive cities from the dataset instead of maintaining a second list (or document why it's a preferred-order hint only)
3. Update ARCHITECTURE.md / SELF-HOSTING.md so fork owners aren't told to edit values that do nothing

Acceptance criteria

• One source of truth per setting; no contradictory copies