reports: total minutes, talk time, answered; outside minutes per day; voip.ms balance

Owner asked for total minutes, call time and missed calls in one place, and the money left on
voip.ms. Reports now totals answered calls, talk time and outside minutes (in from arrival, out
from the answer: roughly what the provider bills), charts outside minutes per day, and shows each
voip.ms trunk's balance (getBalance; verify with a real account).

docs/spec/06-voipms.md

@@ -86,6 +86,10 @@ GET https://voip.ms/api/v1/rest.php
 - Rate limit our sends to 1 per second per DID (queue in memory).
 - Other methods used: `getDIDsInfo` (DID import), `getServersInfo` (server dropdown),
   `getSMS` (optional polling fallback). All behind `voipmsApi(method, params)` with a 15 s timeout.
+- `getBalance` (owner, 2026-10-21: the balance on Reports): `balance.current_balance`, a string
+  like `"12.3456"` in the account's currency **(verify the shape and that the API login needs
+  nothing more, with a real account)**. Each Reports load asks once per voip.ms trunk that has an
+  API login.
 
 ### 5.2 Receiving
 Endpoint: `GET|POST /hooks/voipms/sms/:token`. `:token` is a 32-char random value stored