feat: production hardening v1.2.0

Phase 1 - Licensing & Compliance:
- Add MIT LICENSE file
- Add copyright headers to server/index.js, poller.js, config.js,
  sanitizeError.js, and new loadSecrets.js

Phase 2 - Security Hardening:
- Add server/utils/loadSecrets.js: Docker secrets support via _FILE
  env var pattern (COOKIE_SECRET_FILE, EMBY_API_KEY_FILE, etc.)
- Add SSRF/URL validation in config.js: validates all configured
  service instance URLs for scheme and well-formedness at startup
- Add SIGTERM/SIGINT graceful shutdown: stops poller, drains HTTP
  connections, 10s force-exit fallback
- Warn at startup if COOKIE_SECRET is shorter than 32 characters
- Validate EMBY_URL scheme at startup
- Improve sanitizeError: redact host:port from axios error URLs
  while preserving path/query for other redaction patterns

Phase 3 - Config Robustness:
- Weak COOKIE_SECRET warning (< 32 chars)
- EMBY_URL validated via validateInstanceUrl on startup

Phase 4 - Docker & Deployment:
- .dockerignore: add tests/, coverage/, vitest.config.js,
  CHANGELOG.md, SECURITY.md, LICENSE, .markdownlint.json
- docker-compose.yaml: add commented Option B (Docker secrets
  _FILE pattern) alongside existing plain-env Option A

Phase 5 - Docs & Release Readiness:
- Add CHANGELOG.md with entries from v1.0.0 to v1.2.0
- Update SECURITY.md: supported versions table, fix Docker secrets
  note to reflect _FILE support now implemented
- Add public/.well-known/security.txt for responsible disclosure
- Bump version to 1.2.0

server/utils/sanitizeError.js

@@ -1,3 +1,4 @@
+// Copyright (c) 2025 Gordon Bolton. MIT License.
 // Query-param secrets (SABnzbd apikey, generic token/password params)
 const QUERY_SECRET_PATTERN = /([?&](?:apikey|token|password|api_key|key|secret)=)[^&\s#]*/gi;
 // HTTP auth header values (X-Api-Key, X-MediaBrowser-Token, Authorization, X-Emby-Authorization)
@@ -7,13 +8,18 @@ const HEADER_PATTERN = /(?:x-api-key|x-mediabrowser-token|x-emby-authorization|a
 const BEARER_PATTERN = /bearer\s+[A-Za-z0-9\-._~+/]+=*/gi;
 // Basic auth credentials in URLs (http://user:pass@host)
 const BASIC_AUTH_URL_PATTERN = /\/\/[^:@/\s]+:[^@/\s]+@/gi;
+// Redact only the host:port authority portion of URLs, preserving path/query so
+// other patterns (QUERY_SECRET_PATTERN etc.) can still act on them.
+// Negative lookahead skips URLs already handled by BASIC_AUTH_URL_PATTERN.
+const HOST_PATTERN = /(https?:\/\/)(?!\[REDACTED\]@)([^\s/?#]+)/gi;
 
 function sanitizeError(err) {
   let msg = (err && err.message) ? err.message : String(err);
   msg = msg.replace(QUERY_SECRET_PATTERN, '$1[REDACTED]');
   msg = msg.replace(HEADER_PATTERN, (m) => m.split(/[\s:]/)[0] + ':[REDACTED]');
   msg = msg.replace(BEARER_PATTERN, 'bearer [REDACTED]');
-  msg = msg.replace(BASIC_AUTH_URL_PATTERN, '//[REDACTED]@');
+  msg = msg.replace(BASIC_AUTH_URL_PATTERN, '//[REDACTED]@');  // must run before HOST_PATTERN
+  msg = msg.replace(HOST_PATTERN, '$1[HOST]');
   // Never leak stack traces to API responses
   return msg;
 }