feat(ui): add Sentry Browser SDK client-side integration

- Add 3 new config fields for browser SDK sample rates:
  sentry_js_traces_sample_rate (default 0.0),
  sentry_js_replay_session_sample_rate (default 0.0),
  sentry_js_replay_on_error_sample_rate (default 0.1)
- Expose Sentry config to Jinja2 templates via _inject_global_context;
  empty-string DSN normalized to None so {% if sentry_dsn %} guard works
- Load Sentry Browser SDK bundle.tracing.replay.min.js from the official
  Sentry CDN in base.html when SENTRY_DSN is configured, with Sentry.init()
  for error capture, browser tracing and session replay
- Register new JS settings fields in SETTING_METADATA so they appear on the
  admin Settings → Observability page
- Update .env.demo with commented-out examples for SENTRY_JS_* variables
- Update docs/ConfigurationGuide.md and docs/SentrySetup.md with full
  browser SDK documentation, env-specific examples and troubleshooting
- Add TestSentryJsTemplateContext (5 tests) and TestSentryJsConfig (4 tests)

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>
Agent-Logs-Url: https://github.com/christianlouis/DocuElevate/sessions/4a945567-67df-4264-aaed-75eb2e236e9c

.env.demo

@@ -636,9 +636,26 @@ EMBEDDING_MAX_TOKENS=8000
 # Profiling is only active when SENTRY_TRACES_SAMPLE_RATE > 0. Default: 0.0 (disabled).
 # SENTRY_PROFILES_SAMPLE_RATE=0.0
 #
-# Attach PII (IP addresses, user agents) to Sentry events.
-# Disable (default) to stay GDPR/CCPA compliant.
-# SENTRY_SEND_DEFAULT_PII=false
+# Attach PII (IP addresses, user agents) to Sentry events.
+# Disable (default) to stay GDPR/CCPA compliant.
+# SENTRY_SEND_DEFAULT_PII=false
+#
+# --- Browser (JavaScript) SDK ---
+# The same DSN is reused for the Sentry Browser SDK which is injected into
+# every rendered page.  The DSN is a *public* key and is intentionally
+# embedded in client-side code.
+#
+# Fraction of browser navigations captured for client-side performance tracing.
+# 0.0 (default) disables browser tracing; 1.0 captures every navigation.
+# SENTRY_JS_TRACES_SAMPLE_RATE=0.0
+#
+# Fraction of browser sessions recorded by Sentry Session Replay.
+# 0.0 (default) disables session recording; 1.0 records every session.
+# SENTRY_JS_REPLAY_SESSION_SAMPLE_RATE=0.0
+#
+# Fraction of error sessions recorded by Sentry Session Replay.
+# Defaults to 0.1 (10 %) so errors are captured with replay context.
+# SENTRY_JS_REPLAY_ON_ERROR_SAMPLE_RATE=0.1
 
 # **Mobile App – Push Notifications**
 # Push notifications are delivered via Expo's push notification service