feat(desktop): embed BoosAPI Desktop client as a subproject

Vendor the rebranded BoosAPI Desktop client (Tauri + Vue) into metapi as
a monorepo subdirectory under desktop/. Source only — node_modules,
dist, Cargo target and the upstream .git history are excluded.

desktop/ keeps its own independent Cargo workspace (desktop/src-tauri
with crates/*); it is not part of the backend boosapi crate, so a
`cargo check` at the metapi root still compiles only the backend. Build
the desktop app from desktop/src-tauri per desktop/README.md.

Note: app icons are still placeholder assets pending the final BoosAPI
logo. The updater signing keys live outside the repo and are not
included.

desktop/src-tauri/crates/core/Cargo.toml

@@ -0,0 +1,41 @@
+[package]
+name = "boosapi-core"
+version = "0.0.1"
+edition = "2021"
+
+[dependencies]
+serde = { workspace = true }
+serde_json = { workspace = true }
+sea-orm = { workspace = true }
+tokio = { workspace = true }
+thiserror = { workspace = true }
+uuid = { workspace = true }
+chrono = { workspace = true }
+tracing = { workspace = true }
+anyhow = { workspace = true }
+aes-gcm = "0.10"
+async-trait = "0.1"
+aws-config = { version = "1", features = ["behavior-version-latest"] }
+aws-credential-types = "1"
+aws-sdk-s3 = "1"
+sha2 = "0.10"
+base64 = "0.22"
+reqwest = { version = "0.13", features = ["json", "stream"] }
+futures = "0.3"
+rmcp = { version = "1.2", features = ["client", "transport-child-process", "transport-streamable-http-client-reqwest"] }
+regex = "1"
+hex = "0.4"
+toml_edit = "0.22"
+sqlite-vec = { workspace = true }
+libsqlite3-sys = { workspace = true }
+pdf-extract = "0.7"
+zip = "2"
+litchi = "0.0.1"
+dirs = "5"
+boosapi-migration = { path = "../migration" }
+
+[target.'cfg(target_os = "windows")'.dependencies]
+windows-sys = { version = "0.59", features = ["Win32_System_Threading"] }
+
+[dev-dependencies]
+tempfile = "3"