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.

ingest/internal/grpcserver/server.go

@@ -147,7 +147,12 @@ type AgentOverride struct {
 	HeartbeatEnabled     *bool
 	HeartbeatIntervalMS  *uint64
 	JournaldUnit         *string
-	Version              string
+	// Extra file paths this agent should tail in addition to its local
+	// [source] -- see agent_control.proto's DesiredOverride.
+	// extra_file_paths comment for why this has no "unset" state the
+	// way the pointer fields above do.
+	ExtraFilePaths []string
+	Version        string
 }
 
 func New(logger *slog.Logger, grpcCfg config.GRPCConfig, tlsCfg config.TLSConfig, p batchProducer, resolver TenantResolver, agents AgentRegistry) *Server {
@@ -298,6 +303,7 @@ func (s *Server) CheckIn(ctx context.Context, req *agentv1.CheckInRequest) (*age
 			HeartbeatEnabled:     result.Override.HeartbeatEnabled,
 			HeartbeatIntervalMs:  result.Override.HeartbeatIntervalMS,
 			JournaldUnit:         result.Override.JournaldUnit,
+			ExtraFilePaths:       result.Override.ExtraFilePaths,
 			Version:              result.Override.Version,
 		}
 	}