feat(backend): support des providers OpenCode cloud (#92)

Ajoute le catalogue statique de providers OpenCode (lot B3), le stockage
sécurisé des secrets (SecretStore + adapter infrastructure), et les
use cases SaveOpenCodeProviderProfile/DeleteProfile câblés en composition
root. Couvre le fix B1 et les tests de régression demandés par QA.

cargo build --workspace propre, cargo test --workspace -- --test-threads=1
intégralement vert.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

crates/infrastructure/src/store/mod.rs

@@ -14,6 +14,7 @@ mod memory;
 mod permission;
 mod profile;
 mod project;
+mod secrets;
 mod skill;
 mod template;
 mod vector;
@@ -37,6 +38,7 @@ pub use memory::{index_token_size, FsMemoryStore, NaiveMemoryRecall};
 pub use permission::FsPermissionStore;
 pub use profile::{FsEmbedderProfileStore, FsProfileStore};
 pub use project::FsProjectStore;
+pub use secrets::FsSecretStore;
 pub use skill::FsSkillStore;
 pub use template::FsTemplateStore;
 pub use vector::{should_use_vector, AdaptiveMemoryRecall, VectorMemoryRecall};