The store's layout names live in the core: local::DB_FILE, BLOBS_DIR

"inkwell.db" and "blobs" were spelled out in the ffi and the desktop (whose copy
of DB_FILE sat in the crossover shim). The layout is the core's, the same on
every client, so the names are now core constants and both clients read them.

DRY pass #2, batch 1, F4 (#5372).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

core/src/local/mod.rs

@@ -17,6 +17,12 @@ use std::sync::Mutex;
 
 use rusqlite::Connection;
 
+/// The store's file inside a client's data directory. The layout is the same on
+/// every client, so a store is readable by any client that opens it.
+pub const DB_FILE: &str = "inkwell.db";
+/// Attachment bytes, filed by content hash, beside [`DB_FILE`].
+pub const BLOBS_DIR: &str = "blobs";
+
 /// The shared database handle. rusqlite connections aren't `Sync`, so a `Mutex`
 /// serializes access — fine, since operations are quick and a client is single-user.
 /// How it is held is the caller's business: Tauri manages it as state, Android holds