fix: error-only Sentry telemetry, storm-proof capture, and crash fixes (#476)

Removes Sentry tracing entirely (BullMQ idle polling burned 4.8M transactions in 2 days at the baked 0.1 rate), decouples PostHog sampling, and replaces the type-only error scrub with a vetted-field sanitizer plus SafeError/ToolInputError contracts. One classified capture path with per-signature throttles and a per-process ceiling makes storms impossible (NODE-1E was 4,541 events from one 30s loop). Browser errors move to a dedicated web Sentry project with their own source maps. Adds the SNAPOTTER_TELEMETRY runtime kill switch and silences test fleets.

Crash fixes: remote 204/304 SSRF process kill (NODE-20), conversion-preset boot crash loop (NODE-21), Redis version preflight + unhandled subscribe rejection (NODE-1T), Sign PDF on plain-http origins (NODE-1K/1M), wavesurfer/pdf.js teardown rejections (NODE-1P/1N), bundle-import ZlibError to 400 (NODE-1Z), chart-maker input errors declassified (NODE-1H/1J), asset requests skip the session DB lookup (NODE-1D).

tests/unit/web/tool-feedback-prompt.test.tsx

@@ -42,7 +42,8 @@ beforeEach(() => {
       posthogApiKey: "phc_test",
       posthogHost: "https://us.i.posthog.com",
       sentryDsn: "",
-      sampleRate: 1,
+      sentryDsnWeb: "",
+      posthogSampleRate: 1,
       instanceId: "instance-1",
     },
   });
@@ -70,7 +71,8 @@ describe("ToolFeedbackPrompt", () => {
         posthogApiKey: "",
         posthogHost: "",
         sentryDsn: "",
-        sampleRate: 0,
+        sentryDsnWeb: "",
+        posthogSampleRate: 0,
         instanceId: "",
       },
     });