Remove old architecture support after RN 0.87 update

[NicooleT]

Summary

• Removed Android Paper/old-architecture implementations, generated compatibility classes, architecture flags, and conditional source sets.
• Enabled the React Native Gradle plugin and TurboModule metadata unconditionally.
• Preserved Android React view props and moved required Fabric helpers into the main source set.
• Updated Android event dispatching to the RN 0.87 API.
• Removed legacy iOS views, managers, shadow views, local data, events, and the obsolete Xcode project.
• Made the iOS Fabric components, C++ shadow nodes, and TurboModule implementation unconditional.
• Removed old/new architecture switches from example projects, CI scripts, and the bug-report template.
• Updated the pod lockfile for the New Architecture-only configuration.
• Modernize new arch from fix: replace deep RN imports with public API #744

[janicduplessis]

Heads up on one thing that blocks the 0.82 floor we're planning for 6.x.

getEventDispatcher(context) doesn't exist before RN 0.85

SafeAreaProviderManager.kt#L40 calls the single-arg overload:

UIManagerHelper.getEventDispatcher(reactContext)

That overload landed in 0.85. In 0.82.1 — and in 0.83/0.84 — the only getEventDispatcher is the two-arg (ReactContext, @UIManagerType Int) form, so this is an unresolved-reference compile error on 0.82–0.84.

Suggested fix is the two-arg form rather than going back to getEventDispatcherForReactTag, which is @Deprecated as of 0.87. UIManagerType.FABRIC is public const val FABRIC: Int = 2 in every version 0.82→0.87, and Fabric is the only renderer here now:

import com.facebook.react.uimanager.common.UIManagerType
...
UIManagerHelper.getEventDispatcher(reactContext, UIManagerType.FABRIC)
    ?.dispatchEvent(InsetsChangeEvent(getSurfaceId(reactContext), reactTag, insets, frame))

Peer range

package.json#L59 is >=0.87.0 — should be >=0.82.0 for the intended floor. The compat table in docs/docs/getting-started.mdx also needs a 6.x | >= 0.82 row (it currently stops at 5.x | >= 0.75).

Everything else I checked is 0.82-safe

• Gradle: configureBuildConfigFieldsForLibraries, configureNamespaceForLibraries, and the codegen sourceSets.main.java.srcDir(...) registration are all present in 0.82's ReactPlugin, so dropping buildConfig true, the manifest package attr, and the manual java.directories.add is fine at the floor.
• ViewManager.updateState is still Java with the same @Nullable Object updateState(T, ReactStylesDiffMap, StateWrapper) signature; StateWrapper.updateState(WritableMap) and the 6-arg ReactModuleInfo constructor are identical across 0.82/0.87.
• UIManagerHelper.getReactContext(view) / getSurfaceId(context) both exist in 0.82.
• JS side is fine: CodegenTypes and codegenNativeComponent are both public exports in 0.82's types/index.d.ts, and consumer codegen ≥0.80 handles TSQualifiedName, so the spec rewrites from Update dependencies #753 don't push the floor up.
• iOS/C++ are untouched apart from #ifdef removal and two header swaps — nothing version-sensitive.

Worth noting the example app and CI only run 0.87, so nothing currently exercises the floor — which is why this one slipped through. Some form of multi-version build in CI would catch this class of drift.