feat(attackers): XFF mismatch detection — attacker IP leak bounties

Attackers routinely front their scanners with VPNs/proxies, so the
TCP source we log is the proxy egress, not the real host. But a
surprising number of attacker setups are misconfigured: the proxy
forwards the real IP in an X-Forwarded-For (or Forwarded / X-Real-IP
/ CDN-variant) header. From our side that's a free attribution leak.

New _detect_ip_leak extractor in decnet/web/ingester.py fires at
ingest time per HTTP request. Logic:

1. Require service=http, source_ip present, headers present.
2. If source_ip ∈ DECNET_TRUSTED_PROXIES (comma-separated IPs or
   CIDRs) → legitimate reverse-proxy forwarding, skip.
3. Walk proxy-family headers in priority order: Forwarded (RFC 7239)
   → X-Forwarded-For → X-Real-IP → True-Client-IP → CF-Connecting-IP.
4. Extract the left-most parseable IP from the winning header.
5. If that IP differs from the TCP source → emit a bounty with
   bounty_type="ip_leak" carrying {source_ip, real_ip_claim,
   source_header, headers_seen, path, method}.

Storage is the existing Bounty table — no schema change; de-dup is
handled by Bounty's (attacker_ip, bounty_type, payload_hash) key, so
repeat requests with the same leaked IP don't spam.

AttackerDetail renders a warn-accent "LEAKED IPs:" row under ORIGIN
listing distinct real_ip_claim values; hover tooltip shows the source
header + path of the most recent leak. Only shown when at least one
ip_leak bounty exists.

RFC 7239 Forwarded parser handles the full vocabulary — bare IPv4,
IPv4:port, quoted, IPv6 in brackets, IPv6 with port — returning only
IPs that actually parse.

Closes DEVELOPMENT.md "Network Topology Leakage → X-Forwarded-For
mismatches". Phase 3 of the three-phase Attacker Intelligence series
(phases 1: scanned-vs-interacted, 2: PTR records already shipped).

DECNET_TRUSTED_PROXIES env shape matches THREAT_MODEL DA-08's
"revisit when verified-proxy config lands" note — same token set
future rate-limit work will consume.

decnet_web/src/components/AttackerDetail.tsx

@@ -68,6 +68,20 @@ interface AttackerData {
     interacted: string[];
     scanned: string[];
   };
+  ip_leaks?: Array<{
+    timestamp: string;
+    decky?: string;
+    service?: string;
+    bounty_type: string;
+    payload: {
+      source_ip?: string;
+      real_ip_claim?: string;
+      source_header?: string;
+      headers_seen?: Record<string, string>;
+      path?: string;
+      method?: string;
+    };
+  }>;
 }
 
 // ─── Fingerprint rendering ───────────────────────────────────────────────────
@@ -1027,6 +1041,42 @@ const AttackerDetail: React.FC = () => {
               <span className="dim">—</span>
             )}
           </div>
+          {attacker.ip_leaks && attacker.ip_leaks.length > 0 && (
+            <div>
+              <span className="dim" style={{ color: 'var(--warn, #e0a040)' }}>
+                LEAKED IPs:{' '}
+              </span>
+              {Array.from(
+                new Set(
+                  (attacker.ip_leaks || [])
+                    .map((l) => l.payload?.real_ip_claim)
+                    .filter((v): v is string => !!v),
+                ),
+              ).map((ip, i, arr) => {
+                const latest = (attacker.ip_leaks || []).find(
+                  (l) => l.payload?.real_ip_claim === ip,
+                );
+                const tooltip = latest
+                  ? `${latest.payload.source_header ?? '?'} on ${
+                      latest.payload.method ?? '?'
+                    } ${latest.payload.path ?? '/'}`
+                  : '';
+                return (
+                  <span
+                    key={ip}
+                    style={{
+                      color: 'var(--warn, #e0a040)',
+                      fontFamily: 'monospace',
+                    }}
+                    title={tooltip}
+                  >
+                    {ip}
+                    {i < arr.length - 1 ? ', ' : ''}
+                  </span>
+                );
+              })}
+            </div>
+          )}
         </div>
       </Section>