Fix Swift 6.4 Android linking for SkipFirebaseCore

[michele-theleftbit]

Swift 6.4's default build system rejects Android builds when SkipFirebaseCore is explicitly dynamic while its target is also linked statically.

Keep SkipFirebaseCore's library type automatic when SKIP_BRIDGE is enabled, while retaining dynamic linkage for the other products. Preserve the existing SKIP_BRIDGE activation mechanism and document the Core exception.

Raise minimum dependency versions to skip 1.9.13, skip-foundation 1.4.6, skip-model 1.8.0, skip-ui 1.61.0, and firebase-ios-sdk 12.19.2.

Validation:

• Built an isolated Android consumer with the exact final manifest, Swift 6.4, and the default build system. Generated libSkipFirebaseCore.so and the consumer's shared library.
• Verified library types and dependency minima with SKIP_BRIDGE enabled and disabled; SKIP_DYNAMIC_LIBRARIES alone has no effect.
• git diff --check passed.
• Earlier testing also passed with the native build system and reproduced the original error with updated dependencies but Core explicitly dynamic.