refactor: split the library into fumi-core and make it embeddable

core/Cargo.toml

@@ -0,0 +1,34 @@
+[package]
+name = "fumi-core"
+version = "0.1.0"
+edition = "2021"
+description = "Smol Mail client library: identities, sealing, mailbox operations"
+license = "Apache-2.0"
+
+[features]
+default = ["bundled-sqlite"]
+# Bundle libsqlite3 so the store needs no system SQLite; embedders with their
+# own SQLite (Android's NDK case) build with default-features = false.
+bundled-sqlite = ["rusqlite/bundled"]
+# RNS carrier over microReticulum (RNS.md); needs MICRORETICULUM_SOURCE_DIR
+# at build time, provided by the flake.
+rns = ["dep:cc"]
+
+[dependencies]
+snow = "0.9"
+chacha20poly1305 = "0.10"
+ed25519-dalek = { version = "2", features = ["rand_core"] }
+x25519-dalek = { version = "2", features = ["static_secrets"] }
+sha2 = "0.10"
+hmac = "0.12"
+hkdf = "0.12"
+rand_core = { version = "0.6", features = ["getrandom"] }
+rusqlite = "0.32"
+data-encoding = "2"
+
+[dev-dependencies]
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"
+
+[build-dependencies]
+cc = { version = "1", optional = true }