Phase 16: hardening and release 0.1.0

- TOTP second factor (RFC 6238, secret encrypted under the master key),
  ten hashed single-use recovery codes, two-step login with a pending token
  bound to the client address, account enrolment/disable, admin reset
- tests/security: prompt-injection corpus never acts or creates evidence-free
  beliefs; roles and CSRF on form and API paths; cross-mind isolation
  (demo scenario 5); stored-XSS escaping and CSP across pages; secrets never
  echoed (API, pages, database, archives); hostile archive import; session
  lifecycle and security headers
- OpenAPI 3.1 document generated from the route table, served at
  /api/v1/openapi.json and kept complete by a test
- gosec clean (justified #nosec annotations, cookie/redirect hardening,
  bounded multipart parsing, UUID packing without narrowing conversions);
  govulncheck clean with toolchain pinned to go1.26.8
- THREAT_MODEL verification pointers, SECURITY.md testing section, README,
  CHANGELOG 0.1.0, docs/RELEASE_NOTES.md, PLAN status

internal/ui/study.go

@@ -112,7 +112,8 @@ func (u *UI) snapshotDelete(w http.ResponseWriter, r *http.Request) {
 }
 
 func (u *UI) importArchive(w http.ResponseWriter, r *http.Request) {
-	if err := r.ParseMultipartForm(1 << 20); err != nil {
+	r.Body = http.MaxBytesReader(w, r.Body, snapshots.MaxArchiveBytes+(1<<20))
+	if err := r.ParseMultipartForm(1 << 20); err != nil { // #nosec G120 -- body bounded by MaxBytesReader on the previous line
 		u.flash(w, r, "error", "Upload too large or malformed.", "/minds")
 		return
 	}