feat(firewall): nftables hit-counter pro Regel + Live-Hits-Spalte in der UI

- ruleset.nft.tpl: operator-rules bekommen `counter <action> comment "egid:<id>"`
  → nft zählt Packets + Bytes per Regel ab dem letzten Ruleset-Apply
- handlers/firewall_counters.go: GET /firewall/counters parst
  `sudo nft list table inet edgeguard` per Regex, liefert [{rule_id,packets,bytes}]
- handlers/firewall_counters_test.go: unit-tests für parseNFTCounters
- Firewall/Rules.tsx: neue "Hits"-Spalte (Packet-Count, Tooltip mit Bytes),
  10s-Polling via TanStack Query ['fw','counters']
- i18n de+en: fw.rule.hits

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/handlers/firewall_counters.go

@@ -0,0 +1,63 @@
+package handlers
+
+import (
+	"os/exec"
+	"regexp"
+	"strconv"
+	"strings"
+
+	"github.com/gin-gonic/gin"
+
+	"git.netcell-it.de/projekte/edgeguard-native/internal/handlers/response"
+)
+
+// ruleCounter is one operator-defined firewall rule's live packet/byte
+// counter. The nft ruleset template marks each rule with
+// `counter … comment "egid:<id>"` so we can correlate the counter
+// values back to DB rule IDs.
+type ruleCounter struct {
+	RuleID  int64 `json:"rule_id"`
+	Packets int64 `json:"packets"`
+	Bytes   int64 `json:"bytes"`
+}
+
+var (
+	reEgid    = regexp.MustCompile(`comment "egid:(\d+)"`)
+	reCounter = regexp.MustCompile(`\bcounter packets (\d+) bytes (\d+)\b`)
+)
+
+// Counters reads live hit-counters from the running nft ruleset.
+// Runs `sudo -n /usr/sbin/nft list table inet edgeguard` (already
+// allowed by the postinst sudoers rule) and parses each rule line
+// for the `counter packets N bytes M … comment "egid:X"` pattern
+// that the ruleset template emits.
+func (h *FirewallHandler) Counters(c *gin.Context) {
+	out, err := exec.Command("sudo", "-n", "/usr/sbin/nft", "list", "table", "inet", "edgeguard").CombinedOutput()
+	if err != nil {
+		response.OK(c, gin.H{
+			"counters": []ruleCounter{},
+			"error":    strings.TrimSpace(string(out)),
+		})
+		return
+	}
+	response.OK(c, gin.H{"counters": parseNFTCounters(string(out))})
+}
+
+func parseNFTCounters(output string) []ruleCounter {
+	var out []ruleCounter
+	for _, line := range strings.Split(output, "\n") {
+		mID := reEgid.FindStringSubmatch(line)
+		mCnt := reCounter.FindStringSubmatch(line)
+		if mID == nil || mCnt == nil {
+			continue
+		}
+		id, err1 := strconv.ParseInt(mID[1], 10, 64)
+		pkts, err2 := strconv.ParseInt(mCnt[1], 10, 64)
+		byts, err3 := strconv.ParseInt(mCnt[2], 10, 64)
+		if err1 != nil || err2 != nil || err3 != nil {
+			continue
+		}
+		out = append(out, ruleCounter{RuleID: id, Packets: pkts, Bytes: byts})
+	}
+	return out
+}