feat(waf): Alerts — Regelübereinstimmungen in DB + UI — v1.2.77

- Migration 0038: waf_alerts-Tabelle
- AlertWriter (Buffered-Channel → async DB-Write)
- SPOE: MatchedRules → sendAlert() nach ProcessRequestHeaders()
- API: GET /waf/alerts + DELETE /waf/alerts
- WAF-Page: Tabs Domains | Alarme; Alarme-Tabelle mit Rule-ID,
  Severity, Aktion (Detected/Blocked), URI, Client-IP + Purge-Button

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

internal/database/migrations/0038_waf_alerts.sql

@@ -0,0 +1,20 @@
+-- +goose Up
+CREATE TABLE IF NOT EXISTS waf_alerts (
+    id         BIGSERIAL PRIMARY KEY,
+    domain_id  BIGINT REFERENCES domains(id) ON DELETE CASCADE,
+    hostname   TEXT        NOT NULL,
+    client_ip  TEXT        NOT NULL,
+    method     TEXT        NOT NULL,
+    uri        TEXT        NOT NULL,
+    rule_id    INT         NOT NULL DEFAULT 0,
+    rule_msg   TEXT        NOT NULL DEFAULT '',
+    severity   TEXT        NOT NULL DEFAULT '',
+    action     TEXT        NOT NULL,          -- 'detected' | 'blocked'
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+CREATE INDEX IF NOT EXISTS waf_alerts_domain_created ON waf_alerts(domain_id, created_at DESC);
+CREATE INDEX IF NOT EXISTS waf_alerts_created ON waf_alerts(created_at DESC);
+
+-- +goose Down
+DROP TABLE IF EXISTS waf_alerts;