feat: firewall policy metrics across all output plugins (closes #928) (#979)

* feat(promunifi): add firewall policy metrics (closes #928)

Bump unifi client to v5.22.0 and wire up firewall policy data end-to-end:

- poller.Metrics: add FirewallPolicies []any slice
- inputunifi: collect GetFirewallPolicies() per poll cycle; apply
  DefaultSiteNameOverride; augment into poller.Metrics
- promunifi: export per-rule (rule_enabled, rule_index) and per-site
  aggregate metrics (rules_total, rules_enabled, rules_disabled,
  rules_by_action, rules_predefined, rules_custom, rules_logging_enabled)

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

* feat: export firewall policies to influx, datadog, and otel outputs

Extends firewall policy support (PR #979) to all remaining output plugins:

- influxunifi: batchFirewallPolicy() writes measurement "firewall_policy"
  with tags (rule_name, action, protocol, ip_version, source/dest zone,
  site_name, source) and fields (enabled, index, predefined, logging)
- datadogunifi: batchFirewallPolicy() emits the same data as Datadog gauges
  under the "firewall_policy.*" namespace
- otelunifi: exportFirewallPolicies() emits per-rule gauges
  (unifi_firewall_rule_enabled, unifi_firewall_rule_index) and per-site
  aggregates (rules_total, rules_enabled, rules_disabled, rules_by_action,
  rules_predefined, rules_custom, rules_logging_enabled)

Also rebases onto master to pick up the otelunifi plugin (PR #978).

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

pkg/poller/config.go

@@ -102,6 +102,7 @@ type Metrics struct {
 	DHCPLeases         []any
 	WANConfigs         []any
 	Sysinfos           []any
+	FirewallPolicies   []any
 	ControllerStatuses []ControllerStatus
 }