Final Phase C batch: moves the remaining inline route bodies (12 proxy
stubs, /changelog, the webhooks/hijacks group, PDF export, ASPA adoption
tracker + IPv6 stats endpoints) into server/routes/*.js and
server/services/api-proxy.js, verified byte-for-byte via the smoke-test
diff. Also drops the now-duplicate proxyToApiServer()/API_SERVER_PORT
that were left behind in server.js after api-proxy.js absorbed them.
server.js: 6838 -> 578 lines, under the 800-line project limit.
