feat(web): enforce localhost-only binding; expand loopback origin allow-list (#1796)

Closes #1795.

Enforce localhost-only binding in code (the "never 0.0.0.0" rule was only a spec note): refuse an all-interfaces HOST — across every spelling the OS binds as the wildcard (inet_aton decimal/octal/hex, IPv6, IPv4-mapped, zone-scoped, IDNA/Unicode) — unless DANGEROUSLY_BIND_ALL_INTERFACES=true (Docker's sanctioned opt-in). Fixes the reported stdio-connect 403 by expanding the default loopback origin allow-list to all three interchangeable forms.

Hardening surfaced across an extended review: closes an IDNA/fullwidth wildcard bypass, a blank-ALLOWED_ORIGINS fail-open, and the CLI/TUI OAuth-callback wildcard bind (loopback-only now, RFC 8252); canonicalizes the origin allow-list the way a browser does; derives frame-ancestors from the real embedder list (IPv6-literal exclusion verified in headless Chromium); strictPort on all three bind points; and preserves the CLI exit-code map + JSON envelope through the mcp-inspector --cli launcher path. Shared host normalization lives in core/node/hostUrl.ts. Docs + tests + smokes throughout.

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.gitignore

@@ -8,6 +8,10 @@ clients/web/dist
 clients/**/build
 clients/**/coverage
 test-servers/build
+# TypeScript incremental build cache (written by `tsc -b`); web routes its own
+# into node_modules/.tmp via tsBuildInfoFile, but a stray `tsc -b` elsewhere
+# drops one next to the tsconfig — never source.
+*.tsbuildinfo
 .env
 /.playwright-mcp/