Add local login, agent extra log paths, IPv4/IPv6 metrics; remediate security audit findings

This is a large squashed commit covering two batches of prior uncommitted
work plus a full security-audit remediation pass, kept together because
go.mod/go.sum and several shared files (main.go, handler.go) were touched
by both and splitting risked non-building intermediate commits.

Features (built earlier, previously uncommitted):
- Local username/password login for single-tenant deployments with no
  SSO configured (api/localauth, alerting/internal/sessioncheck,
  sentryctl users, web/src/routes/login, metadata migrations 0040/0041).
- Remotely-editable additional log file paths for agents, on top of
  their existing primary source (api/agents, agent/sentry-agent
  extra-file-path diffing, web agent config UI).
- IPv4/IPv6 addresses reported alongside other host system metrics.

Security audit remediation (this pass, all live-verified in production):
- Critical: block ClickHouse SSRF table functions (url/remote/file/s3/...)
  in the raw-SQL query escape hatch.
- High: deny sensitive paths and require Admin to add agent
  extra_file_paths (Editor could previously point an agent at /etc/shadow
  or an SSH key); alerting webhook targets now validate against
  internal/metadata/loopback addresses, both at creation and send time;
  alerting's session middleware now enforces an Editor+ floor on
  mutating requests instead of "any authenticated session"; bumped
  goxmldsig to close a SAML signature-verification bypass (GO-2026-4753).
- Medium: per-IP login rate limiting; security response headers
  (HSTS/CSP/nosniff/X-Frame-Options/Referrer-Policy/Permissions-Policy)
  on web/nginx.conf; a DevCredentialWarnings check in every Go service's
  config loader, logging loudly at startup if a deployment is still on
  docker-compose.yml's literal dev-only credentials; dependency bumps
  (golang.org/x/text, grpc, x/net, quick-xml, h2) across every affected
  Go module and both Rust crates, including a previously-uncovered x/net
  vulnerability in deploy/operator; a new security-scan.yml CI workflow
  running cargo-deny/govulncheck/npm-audit, mirroring the existing
  license-compliance.yml matrix shape.
- Low: removed sentryctl's plaintext --password flag (shell
  history/`ps` exposure) in favor of stdin and a --password-stdin flag
  for reset-password's optional specific-password path; a dummy bcrypt
  comparison closes a login response-time username-enumeration
  side-channel.

alerting/cmd/alerting/main.go

@@ -29,6 +29,7 @@ import (
 	"github.com/sentry/sentry/alerting/internal/notifystore"
 	"github.com/sentry/sentry/alerting/internal/queryclient"
 	"github.com/sentry/sentry/alerting/internal/rulestore"
+	"github.com/sentry/sentry/alerting/internal/sessioncheck"
 )
 
 func main() {
@@ -39,6 +40,9 @@ func main() {
 		logger.Error("loading config", "error", err)
 		os.Exit(1)
 	}
+	for _, w := range cfg.DevCredentialWarnings() {
+		logger.Warn(w)
+	}
 
 	// -healthcheck: self-check mode for Docker's HEALTHCHECK, mirrors
 	// api/cmd/api/main.go's runHealthcheck -- this image is distroless too
@@ -71,9 +75,23 @@ func main() {
 	handler := httpapi.NewHandler(logger, rules, targets, rules)
 	mux := http.NewServeMux()
 	handler.RegisterRoutes(mux)
+
+	// Local login (see /docs -- deployment runbook, and
+	// api/localauth's package doc comment for the full feature):
+	// alerting has no per-route role plumbing of its own, so this is one
+	// blanket "must have a valid session" gate in front of the whole
+	// mux, same shape CORS already wraps it in below. /healthz stays
+	// reachable regardless -- see sessioncheck.RequireSession's doc
+	// comment.
+	var gatedMux http.Handler = mux
+	corsFn := httpserver.WithCORS
+	if cfg.LocalAuthEnabled {
+		gatedMux = sessioncheck.RequireSession(sessioncheck.NewChecker(pgPool), mux)
+		corsFn = httpserver.WithCredentialedCORS
+	}
 	srv := &http.Server{
 		Addr:    cfg.HTTPListenAddr,
-		Handler: httpserver.WithCORS(mux, cfg.CORSAllowedOrigin),
+		Handler: corsFn(gatedMux, cfg.CORSAllowedOrigin),
 	}
 
 	eval := evaluator.New(rules, targets, qc, cfg.Evaluator.QueryTimeout, cfg.Evaluator.ClaimBatchSize, cfg.Evaluator.WorkerPoolSize, logger)