The README's quotas paragraph says the apps limit is enforced and the repositories limit is not yet #2167

Replaces #2152. Its premise is true now that #2136 (d0fa1bc9) is on main.

Done looks like:

• [ ] README.md, the quotas paragraph (around line 1122, which ends "Nothing enforces a quota yet: no create path reads one."): that sentence is replaced by what src/actions/app_limit.ts and its callers enforce on main. A set apps limit refuses one more app unless the actor is a forge admin. Give the status and the error each door answers, read from the code and its test, not copied from this issue. Then say that repositories is not enforced yet (#2093).
• [ ] The doc comment in src/settings/quotas.ts is rewrapped to the module's line width.
• [ ] bun x tsc --noEmit passes. No behaviour changes, so no new test is needed.

Brief: scout.