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.

api/agents/handler_test.go

@@ -199,6 +199,116 @@ func TestHandleSetConfigRejectsTooSmallHeartbeatInterval(t *testing.T) {
 	}
 }
 
+func TestHandleSetConfigExtraFilePathsRoundTrips(t *testing.T) {
+	s := newFakeStore()
+	s.put(Agent{TenantID: "default", Host: "web-01"})
+	h := newTestHandler(s)
+
+	rec := doRequest(t, h, "PUT", "/agents/web-01/config", ConfigOverride{
+		ExtraFilePaths: []string{"/var/log/nginx/access.log", "/var/log/nginx/error.log"},
+	})
+	if rec.Code != http.StatusOK {
+		t.Fatalf("status = %d, want 200, body=%s", rec.Code, rec.Body.String())
+	}
+	var got Agent
+	if err := json.Unmarshal(rec.Body.Bytes(), &got); err != nil {
+		t.Fatalf("decoding response: %v", err)
+	}
+	if got.DesiredOverride == nil || len(got.DesiredOverride.ExtraFilePaths) != 2 {
+		t.Fatalf("unexpected override: %+v", got.DesiredOverride)
+	}
+}
+
+func TestHandleSetConfigRejectsRelativeExtraFilePath(t *testing.T) {
+	s := newFakeStore()
+	s.put(Agent{TenantID: "default", Host: "web-01"})
+	h := newTestHandler(s)
+
+	rec := doRequest(t, h, "PUT", "/agents/web-01/config", ConfigOverride{
+		ExtraFilePaths: []string{"relative/path.log"},
+	})
+	if rec.Code != http.StatusBadRequest {
+		t.Fatalf("status = %d, want 400", rec.Code)
+	}
+}
+
+func TestHandleSetConfigRejectsTooManyExtraFilePaths(t *testing.T) {
+	s := newFakeStore()
+	s.put(Agent{TenantID: "default", Host: "web-01"})
+	h := newTestHandler(s)
+
+	paths := make([]string, 21)
+	for i := range paths {
+		paths[i] = "/var/log/x.log"
+	}
+	rec := doRequest(t, h, "PUT", "/agents/web-01/config", ConfigOverride{ExtraFilePaths: paths})
+	if rec.Code != http.StatusBadRequest {
+		t.Fatalf("status = %d, want 400", rec.Code)
+	}
+}
+
+// TestHandleSetConfigDenylistsSensitivePaths is the regression test for
+// the security-audit finding that a root, unsandboxed agent plus an
+// unrestricted extra_file_paths let any Editor read arbitrary files
+// (e.g. /etc/shadow, SSH keys) and have them shipped into ClickHouse.
+func TestHandleSetConfigDenylistsSensitivePaths(t *testing.T) {
+	denied := []string{
+		"/etc/shadow",
+		"/etc/passwd",
+		"/root/.bash_history",
+		"/home/alice/.ssh/id_rsa",
+		"/home/alice/.ssh/authorized_keys",
+		"/proc/1/environ",
+		"/etc/sentry-agent/client-key.pem",
+		"/opt/app/../../etc/shadow",
+		"/opt/app/id_ed25519",
+	}
+	for _, p := range denied {
+		s := newFakeStore()
+		s.put(Agent{TenantID: "default", Host: "web-01"})
+		h := newTestHandler(s)
+		rec := doRequest(t, h, "PUT", "/agents/web-01/config", ConfigOverride{ExtraFilePaths: []string{p}})
+		if rec.Code != http.StatusBadRequest {
+			t.Errorf("path %q: status = %d, want 400 (should be denylisted), body=%s", p, rec.Code, rec.Body.String())
+		}
+	}
+}
+
+// TestHandleSetConfigExtraFilePathsRequiresAdminToAdd is the regression
+// test for the audit's role-floor fix: adding/changing extra_file_paths
+// needs Admin, not just Editor, since it grants the agent read access to
+// a new file. Purely shrinking or clearing an existing set stays at the
+// Editor floor everything else in this override uses.
+func TestHandleSetConfigExtraFilePathsRequiresAdminToAdd(t *testing.T) {
+	s := newFakeStore()
+	s.put(Agent{TenantID: "default", Host: "web-01"})
+	editor := NewHandler(discardLogger(), s, fakeAuthorizer{role: authz.RoleEditor}, nil)
+	admin := NewHandler(discardLogger(), s, fakeAuthorizer{role: authz.RoleAdmin}, nil)
+
+	rec := doRequest(t, editor, "PUT", "/agents/web-01/config", ConfigOverride{
+		ExtraFilePaths: []string{"/var/log/nginx/access.log"},
+	})
+	if rec.Code != http.StatusForbidden {
+		t.Fatalf("editor adding a path: status = %d, want 403", rec.Code)
+	}
+
+	rec = doRequest(t, admin, "PUT", "/agents/web-01/config", ConfigOverride{
+		ExtraFilePaths: []string{"/var/log/nginx/access.log", "/var/log/nginx/error.log"},
+	})
+	if rec.Code != http.StatusOK {
+		t.Fatalf("admin adding paths: status = %d, want 200, body=%s", rec.Code, rec.Body.String())
+	}
+
+	// Shrinking back down to one path is a pure removal -- Editor should
+	// be allowed to do this even though they couldn't have added it.
+	rec = doRequest(t, editor, "PUT", "/agents/web-01/config", ConfigOverride{
+		ExtraFilePaths: []string{"/var/log/nginx/access.log"},
+	})
+	if rec.Code != http.StatusOK {
+		t.Fatalf("editor removing a path: status = %d, want 200, body=%s", rec.Code, rec.Body.String())
+	}
+}
+
 func TestHandleSetConfigUnknownHostIsNotFound(t *testing.T) {
 	h := newTestHandler(newFakeStore())
 	interval := int64(30000)