Remove the call-home usage reporter (#4759)

Completely removes the call-home reporter, so Electric no longer sends
anonymous usage data to checkpoint.electric-sql.com.

## What's removed

- `ElectricTelemetry.CallHomeReporter`, its `Reporters.CallHomeReporter`
wrapper, and the `Measurement` aggregation helper that existed solely to
compute the call-home report percentiles, along with the `req`, `bypass`
and `ex_json_schema` dependencies they pulled into `electric-telemetry`.
- The `ELECTRIC_USAGE_REPORTING` and `ELECTRIC_TELEMETRY_URL`
environment variables, the `call_home_telemetry?` / `telemetry_url`
configuration options for embedded use, and
`Electric.Config.parse_telemetry_url/1`.
- The `installation_id` telemetry option — the call-home reporter's
static info was its only consumer. The id itself is still persisted in
the KV store and picked up by the OTel resource detector.
- The "Anonymous usage data" section of the telemetry docs and the
"Usage reporting" section of the configuration docs.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

Author: alco

.changeset/remove-call-home-reporter.md

@@ -0,0 +1,6 @@
+---
+"@core/sync-service": patch
+"@core/electric-telemetry": patch
+---
+
+Remove the call-home reporter that sent anonymous usage data to checkpoint.electric-sql.com. Electric no longer phones home; the `ELECTRIC_USAGE_REPORTING` and `ELECTRIC_TELEMETRY_URL` environment variables are gone, along with the `call_home_telemetry?` and `telemetry_url` configuration options for embedded use.

packages/electric-telemetry/lib/electric/telemetry.ex

@@ -35,7 +35,6 @@ defmodule ElectricTelemetry do
   def export_enabled?(%{reporters: reporters}) do
     truthy?(
       reporters.statsd_host ||
-        reporters.call_home_url ||
         reporters.otel_metrics? ||
         reporters.prometheus?
     )

packages/electric-telemetry/lib/electric/telemetry/application_telemetry.ex

@@ -47,10 +47,6 @@ defmodule ElectricTelemetry.ApplicationTelemetry do
     prometheus_metrics = metrics ++ Map.get(opts, :additional_prometheus_metrics, [])
 
     [
-      Reporters.CallHomeReporter.child_spec(
-        opts,
-        metrics: Reporters.CallHomeReporter.application_metrics()
-      ),
       Reporters.Otel.child_spec(opts, metrics: metrics),
       Reporters.Prometheus.child_spec(opts, metrics: prometheus_metrics),
       Reporters.Statsd.child_spec(opts, metrics: metrics)

packages/electric-telemetry/lib/electric/telemetry/call_home_reporter.ex

@@ -243,7 +243,7 @@ defmodule ElectricTelemetry.EtsTables do
       String.contains?(name_string, ":") ->
         extract_type_with_separator(name_string, ":", @uuid_pattern)
 
-      # Pattern 2: name_stack_id (e.g., "stack_call_home_telemetry_6dd7c00b-8")
+      # Pattern 2: name_stack_id (e.g., "stack_otel_telemetry_6dd7c00b-8")
       # Extract everything before the last underscore that precedes a UUID-like pattern
       String.contains?(name_string, "_") ->
         extract_type_with_separator(name_string, "_", @uuid_pattern)