Quotas: reset one address, or give some back

POST /rules/{ref}/reset-quota takes an optional address (one entry of a
per-address quota starts again) and give (bytes taken off what was used,
one address's or everyone's, until the next reset). The firewall keeps
the adjustment for its next apply, which writes the new usage into the
ruleset; housecarld applies at once and saves the usage. hc rule
reset-quota --address/--give; Reset and Give back in the web UI, per
address in the usage dialog.

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

docs/rules.md

@@ -186,8 +186,17 @@ hc rule add forward --in lan --out wan --quota 50gbytes,over,per-source,monthly=
 hc rule add forward --in guest --out wan --quota 10gbytes,over,daily -a drop
 hc quotas                      # what each used, and the next reset
 hc rule reset-quota 31         # start again now
+hc rule reset-quota 31 --address 192.168.1.23            # one device only
+hc rule reset-quota 31 --give 5gbytes --address 192.168.1.23
 ```
 
+`--give` is a top-up: it takes that much off what was used (never below
+zero), so the device gets 5 GB more until the quota's next reset, and the
+rule stays as it is. The web UI has **Reset** and **Give back…** on the
+rule, and for each address in its usage dialog. Like a reset, these are
+done at once (audited, not staged or on probation); Housecarl puts the
+ruleset in force again with the new figure.
+
 In the web UI each quota's use is on its rule (with **Reset**), all of
 them together on the dashboard, and their history under **Traffic →
 Statistics**.