[Feat] add soroban chain type

[RogerKSI]

Fixed: #XXXX

Implementation details

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[Copilot]

Pull request overview

Adds Soroban (Stellar) as a supported destination chain type in the relayer, wiring up a Soroban chain provider, remote-only wallet signing via FKMS, and DB/proto updates to carry the new chain type end-to-end.

Changes:

• Introduces ChainTypeSoroban plus a new Soroban chain provider (client/config/provider) and Soroban remote-only wallet signer.
• Extends FKMS protobuf + generated stubs/mocks with SignSoroban RPC and SOROBAN chain type.
• Updates storage/config/db migrations to recognize soroban and pulls in Stellar SDK + dependency updates.

Reviewed changes

Copilot reviewed 16 out of 17 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
relayer/wallet/soroban/wallet.go	Adds Soroban wallet constructor using remote-only adapter.
relayer/wallet/soroban/types.go	Defines Soroban signer payload model used for remote signing.
relayer/wallet/soroban/remote_signer.go	Implements FKMS-backed Soroban remote signer calling SignSoroban.
relayer/store/filesystem.go	Wires Soroban wallet creation into filesystem store factory.
relayer/db/migrations/sqlite/00001_create_transactions.sql	Expands SQLite chain_type CHECK constraint to include soroban (and others).
relayer/db/migrations/postgres/00005_add_soroban_chain_type.sql	Adds soroban value to Postgres chain_type enum.
relayer/config/config.go	Enables parsing Soroban chain provider configs.
relayer/chains/types/chain_type.go	Adds Soroban to chain type enum + string mappings.
relayer/chains/soroban/config.go	Defines Soroban chain provider config fields.
relayer/chains/soroban/client.go	Implements Horizon-based client pool, balance/tx queries, broadcast.
relayer/chains/soroban/provider.go	Implements Soroban packet relay flow, metrics, DB persistence.
proto/fkms/v1/signer.proto	Adds Soroban signing RPC + payload messages + enum value.
proto/fkms/v1/signer.pb.go	Updates generated protobuf Go types for Soroban additions.
proto/fkms/v1/signer_grpc.pb.go	Updates generated gRPC client/server interfaces for SignSoroban.
internal/relayertest/mocks/signer_grpc.go	Extends gomock stubs with SignSoroban.
go.mod	Adds Stellar SDK, bumps toolchain + dependency versions.
go.sum	Records new/updated module checksums.

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[Copilot]

Pull request overview

Copilot reviewed 16 out of 17 changed files in this pull request and generated 4 comments.

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[Copilot]

Pull request overview

Copilot reviewed 19 out of 20 changed files in this pull request and generated 5 comments.

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