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.

enterprise/internal/config/config.go

@@ -37,6 +37,36 @@ type Config struct {
 	CORSAllowedOrigin string
 }
 
+// devOnlyCredential is docker-compose.yml's zero-config default for
+// every Postgres/ClickHouse password in this repo -- see
+// api/internal/config.Config.DevCredentialWarnings for the full
+// reasoning (duplicated here per this repo's no-shared-code-between-
+// services convention). enterprise-auth also has its own dev-only
+// literal for ENTERPRISE_SESSION_SIGNING_KEY, checked alongside it below
+// -- per the threat model doc, this is "the single highest-value secret
+// in the enterprise deployment," since compromising it lets an attacker
+// forge any identity, including the RoleService credential.
+const (
+	devOnlyCredential = "sentry-dev-only"
+	devOnlySigningKey = "sentry-dev-only-session-signing-key-32bytes+"
+)
+
+// DevCredentialWarnings reports which configured secrets still equal
+// their literal dev-only defaults -- cmd/enterprise-*/main.go logs each
+// one loudly at startup. A warning, not a startup-refusing error: local
+// dev's zero-config docker-compose.yml path legitimately leaves these
+// at their default values.
+func (c Config) DevCredentialWarnings() []string {
+	var warnings []string
+	if c.Postgres.Password == devOnlyCredential {
+		warnings = append(warnings, "POSTGRES_PASSWORD is still the default dev-only value -- set a real password before this is reachable outside local dev")
+	}
+	if string(c.SessionSigningKey) == devOnlySigningKey {
+		warnings = append(warnings, "ENTERPRISE_SESSION_SIGNING_KEY is still the default dev-only value -- this is the single highest-value secret in an enterprise deployment (compromise lets an attacker forge any identity); set a real, random one before this is reachable outside local dev")
+	}
+	return warnings
+}
+
 type PostgresConfig struct {
 	Addr     string
 	Database string