Add repository opening loading overlay

Introduce a full-screen, animated overlay to provide visual feedback
when the application is opening a repository. This prevents perceived
delays and informs the user about the ongoing operation.

Also, enhance build performance and binary size by configuring
Cargo profiles:
- Development: Enable incremental compilation, use line-tables-only
  debug info, and optimize third-party dependencies to speed up
  rebuilds and improve runtime snappiness during development.
- Release: Apply aggressive optimizations (opt-level 3, thin LTO,
  single codegen unit, stripping) for smaller, faster binaries.

src-tauri/Cargo.toml

@@ -18,3 +18,24 @@ tauri-build = { version = "2", features = [] }
 
 [target.'cfg(not(any(target_os = "android", target_os = "ios")))'.dependencies]
 tauri-plugin-updater = "2"
+
+# ── Build profiles ───────────────────────────────────────────────────────────
+# Dev: keep incremental compilation and emit only line-table debug info instead
+# of full debuginfo. This cuts link time noticeably (linking is the slow part of
+# a `tauri dev` recompile) while still giving panic backtraces with line numbers.
+[profile.dev]
+incremental = true
+debug = "line-tables-only"
+
+# Optimize third-party dependencies once (they are cached), so the running dev
+# build is snappy without slowing down rebuilds of our own crate.
+[profile.dev.package."*"]
+opt-level = 2
+
+# Release: smaller binary (also shrinks the auto-updater download) without
+# regressing runtime performance of the code-search feature.
+[profile.release]
+opt-level = 3
+lto = "thin"
+codegen-units = 1
+strip = true