fix(bindings,ci): Remove unsafeFlags from swift publish

[DaughterOfMars]

Summary

Fixes make swift-release-example, which currently errors with:

error: 'release': the target 'IotaSDK' in product 'IotaSDK' contains unsafe build flags

The published Package.swift on iotaledger/iota-sdk-swift carries a linkerSettings: [.unsafeFlags(["-L", "Sources/CIotaSDK", "-liota_sdk_ffi"])] clause on the IotaSDK target. SwiftPM forbids consuming a package whose targets declare .unsafeFlags(...), so any downstream consumer (including the release example) is broken. The flags were a side-effect of the publish workflow archiving the local-dev bindings/swift/Package.swift verbatim and overwriting the consumer repo's Package.swift with it on every release — the comment in that file claiming the published copy uses an XCFramework was aspirational.

This PR makes that comment true: the publish flow now builds an XCFramework from the per-target dylibs and ships a clean Package.swift that references it via .binaryTarget. The local-dev Package.swift (still using .unsafeFlags for fast in-repo iteration) is unchanged.

Changes

bindings/swift/dist/ (new)

• Package.swift — the manifest that gets written into iota-sdk-swift on publish. Uses .binaryTarget(name: "CIotaSDK", path: "IotaSDK.xcframework"), drops the example targets and .unsafeFlags.
• module.modulemap — bundled into each XCFramework slice's Headers/.

.github/workflows/swift_publish.yml

• New xcframework job: lipos the macOS x86_64 + arm64 dylibs into a universal slice, then xcodebuild -create-xcframework over the macOS fat lib + iOS device dylib + iOS-sim dylib. Produces IotaSDK.xcframework as an artifact.
• release-archives now consumes xcframework (instead of prepare-libraries-archives directly), copies dist/Package.swift over the local-dev one, removes Sources/CIotaSDK, lib, and dist before commit.
• prepare-source-archive now ships bindings/swift/dist instead of bindings/swift/Package.swift.
• prepare-libraries-archives matrix simplified: runs-on: macos-latest hoisted out of every entry, and the constant lib: libiota_sdk_ffi.dylib field is gone (inlined where used).

.github/workflows/{swift,csharp,go}_publish.yml

• if: guards on prepare-libraries-archives standardized from contains(tag_name, ...) to startsWith(tag_name, ...), matching the source-archive jobs and being precise about the tag prefix format.