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/config/config.go

@@ -62,7 +62,7 @@ func Defaults() Config {
 func Load(path string, lookup func(string) (string, bool)) (Config, error) {
 	c := Defaults()
 	if path != "" {
-		b, err := os.ReadFile(path)
+		b, err := os.ReadFile(path) // #nosec G304 -- operator-supplied config path from the command line
 		if err != nil {
 			return c, fmt.Errorf("config: read %s: %w", path, err)
 		}