[burhankhanzada]

What and why

Windows and Linux users were never counted. The Firebase Flutter SDK has no Windows/Linux implementation, so TelemetrySupport.analytics was false there and those installs sent nothing. AnalyticsService now sends through an AnalyticsBackend: the Firebase SDK where it exists, and the GA4 Measurement Protocol (lib/core/telemetry/measurement_protocol.dart) on Windows/Linux, into the same property, under the same consent. Nothing is created, not even the client ID, until the user agrees. An edition supplies the stream through the new optional TelemetryConfig.measurementProtocol; TelemetryConfig.firebase is now optional too.

On Windows/Linux, the backend handles the parts the SDK normally does:

• Users: a random client ID per install. GA4 refuses first_visit over the protocol, so a new ID sends first_launch instead.
• Sessions and active users: every event carries session_id, which renews after 30 minutes idle, and engagement_time_msec, capped at 1 minute. GA4 needs both to count the user as active.
• Screens: sent as page_view, because web streams refuse screen_view.
• Batching: events are sent 25 at a time or every 10 s, and flushed on exit. A failed send is dropped, not retried.
• Consent withdrawn: anything unsent is dropped.
• Debug builds: post to /debug/mp/collect, which validates and records nothing.

Also in this PR:

• Fixed: every analytics report said version 0.0.1. app_version came from a constant that never moved. It is now read from the build (PackageInfo), and OpenTelemetry's service.version gets the same value.
• New user property: signed_in (yes/no, never the account).
• New milestones: first_template_open, first_component_added, first_compile_attempt.
• User properties are re-sent when consent is given mid-session. Theme was only ever set at startup, while analytics was still off. Consent is now applied before the answer is published, so listeners find analytics already on.
• Flush on exit: buffered analytics is flushed on exit alongside OpenTelemetry.
• Unrelated commit (b129760): a dragged part's wires follow it live. The drag edited the lists in place, and the wire painter only repaints when it is handed a new list.

Merge before PinBench/pro#6 (pro depends on pinbench_edition_api at main).

How it was verified

• flutter analyze: clean
• dart format lib test: no changes
• flutter test: 579 passed, 7 skipped. That includes 13 new tests in test/core/telemetry/measurement_protocol_test.dart (sessions, engagement, batching, consent, client-ID persistence, request shape) and the new drag test.
• Tried it in the running app. It hasn't been run on Windows/Linux yet, because that needs the GA stream and secret (see the pro PR).

Notes for the reviewer

• Measurement Protocol data has no geography (the protocol doesn't geolocate the sender). Windows/Linux new users show up as the first_launch event, not in GA's "New users" metric.
• To use the new properties in reports, register signed_in and the existing run_platform, app_version, theme and entry_mode as user-scoped custom dimensions in GA4. Mark the first_* milestones as key events.

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