docs: boost via economy temperature as the first command

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/spec.md

@@ -57,8 +57,10 @@ Functional:
 
 - F1 Live status of all verified readings.
 - F2 History for the last 7 days.
-- F3 Change allowlisted settings. First and most important: heat hot water (CWU) earlier or later
-  than the weekly program (the only thing my parents use the Frisko app for).
+- F3 Change allowlisted settings. First and most important, **boost**: heat hot water (CWU) or
+  the house (CO) outside the weekly program. Today my father does it in the Frisko app by raising
+  the economy temperature (CWU 4143, CO 4131) and lowering it later. Our boost raises it for a
+  chosen time and restores the previous value automatically.
 - F4 Alarms shown in the app, with notification on a new alarm.
 - F5 Health of backend, controller link and tunnel.