fix(ios): let the watch companion build for the simulator without a team

[formed2forge]

Summary

A contributor with no Apple developer account couldn't run the app on the iOS simulator — normally the account-free on-ramp — because the watch companion target (omiWatchApp) requires a development team even for a simulator destination:

Error (Xcode): No Account for Team "9536L8KLMP". Add a new account in Accounts settings...
Error (Xcode): No profiles for '...development.watchapp' were found

Root cause

Root-caused with -showBuildSettings and the real build log's tool invocations, not guessed. Two hypotheses were tested and ruled out first:

• A missing watchOS simulator runtime looked promising (my machine had none installed) but was disproven with a clean rebuild after installing the runtime and pairing a watch simulator to the test device — the watch target's resolved SDKROOT was still the device WatchOS SDK, confirmed both via -showBuildSettings and the ExecuteExternalTool ... -isysroot .../WatchOS.platform/... lines in the actual build log.
• A Base.xcconfig-level CODE_SIGNING_ALLOWED[sdk=*simulator*] = NO override (an earlier attempt) never matched anything, for the same reason: the watch target's own resolved SDK isn't a simulator SDK even when the overall scheme destination is a simulator, so an SDK-qualified condition can't distinguish this build from a genuine device build.

Fix

Since Runner and the widget already build for the simulator without a signing identity, and the watch companion target is SKIP_INSTALL = YES (it's only ever embedded in Runner.app, never independently installed), disabling signing specifically for its dev-flavor configurations is safe:

• Does not touch Runner's or the widget's signing at all.
• Does not affect prod/beta, where the watch app may still need real signing for distribution.

Testing

No automated test — this is an Xcode project-settings fix with no Linux-CI-reachable seam (Dart Analyze & Tests runs on Ubuntu, where Xcode doesn't exist), consistent with how #7641's signing changes were verified: manually, on macOS, with a real build.

Verified live and reproducibly, from a fully clean DerivedData:

• Raw xcodebuild using the exact invocation flutter run constructs (-allowProvisioningUpdates -allowProvisioningDeviceRegistration -workspace ... -scheme dev -destination id=<simulator>) → ** BUILD SUCCEEDED **.
• The real flutter run --flavor dev -d <simulator> → Launching lib/main.dart on iPhone 17 Pro in debug mode... — no signing errors, with the exact same team (9536L8KLMP) this machine has no account for.

Failure-Class: none

Fixes #11776.

[formed2forge]

All CI checks are green and this is ready for maintainer review/merge — I don't have write access to merge it myself.

Summary: the watch companion target (omiWatchApp) required a development team even for simulator builds, blocking the account-free on-ramp for contributors without an Apple developer account. Root-caused with -showBuildSettings and the real build log (two other hypotheses — missing watchOS simulator runtime, an SDK-scoped xcconfig override — were tested and ruled out first, both documented in the PR description). Fix disables signing only on the watch target's dev-flavor configs, directly in project.pbxproj; Runner/widget signing and prod/beta are untouched. Verified live and reproducibly with the exact invocation flutter run constructs.

[kodjima33]

Three-line dev-flavor signing fix for the watch companion so simulator builds work without a team; root-caused with -showBuildSettings, prod/beta signing untouched. Fixes #11776.