Decouple core Yaak logic from Tauri (#354)

crates/yaak-models/blob_migrations/00000000000000_init.sql

@@ -0,0 +1,12 @@
+CREATE TABLE body_chunks
+(
+    id          TEXT PRIMARY KEY,
+    body_id     TEXT    NOT NULL,
+    chunk_index INTEGER NOT NULL,
+    data        BLOB    NOT NULL,
+    created_at  DATETIME DEFAULT (STRFTIME('%Y-%m-%d %H:%M:%f', 'NOW')) NOT NULL,
+
+    UNIQUE (body_id, chunk_index)
+);
+
+CREATE INDEX idx_body_chunks_body_id ON body_chunks (body_id, chunk_index);