Initial commit: MTG personal library catalog (Tauri v2 + React/TS)

Full working app with:
- Rust core (mtgc-core): Scryfall ingester, nucleo fuzzy search, SQLite two-DB
  architecture (reference.db + library.db via ATTACH), criteria filters, deck ops
- Tauri v2 shell exposing the core as typed IPC commands
- React/TS frontend: card entry, library browser, deck editor
- Features: fuzzy card search, color/CMC/type/commander-identity filters,
  tile/list view toggle, hover card previews, deck format + commander support,
  per-card location field, grouping by type/subtype/CMC/color, localStorage
  persistence for active tab/deck/grouping, Discord-inspired dark UI (#C8553D accent)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

crates/mtgc-core/src/error.rs

@@ -0,0 +1,29 @@
+//! Core error type.
+
+use thiserror::Error;
+
+#[derive(Debug, Error)]
+pub enum CoreError {
+    #[error(transparent)]
+    Sqlite(#[from] rusqlite::Error),
+
+    #[error(transparent)]
+    Io(#[from] std::io::Error),
+
+    #[error("http error: {0}")]
+    Http(String),
+
+    #[error("json error: {0}")]
+    Json(#[from] serde_json::Error),
+
+    #[error("{0}")]
+    Other(String),
+}
+
+pub type Result<T> = std::result::Result<T, CoreError>;
+
+impl From<ureq::Error> for CoreError {
+    fn from(e: ureq::Error) -> Self {
+        CoreError::Http(e.to_string())
+    }
+}