Refine semantic search and CPU fallback

- make Candle CUDA support opt-in so default builds work on CPU-only machines
- improve semantic search loading and empty states in the gallery
- keep semantic search UX clearer when no matches are found

Refs: #4

src-tauri/Cargo.toml

@@ -12,6 +12,10 @@ crate-type = ["staticlib", "cdylib", "rlib"]
 [build-dependencies]
 tauri-build = { version = "2", features = [] }
 
+[features]
+default = []
+candle-cuda = ["candle-core/cuda", "candle-nn/cuda", "candle-transformers/cuda"]
+
 [dependencies]
 tauri = { version = "2", features = ["protocol-asset"] }
 tauri-plugin-opener = "2"
@@ -35,8 +39,8 @@ log = "0.4"
 ffmpeg-sidecar = "2.5.0"
 xxhash-rust = { version = "0.8", features = ["xxh3"] }
 sysinfo = "0.38.4"
-candle-core = { version = "0.10.2", features = ["cuda"] }
-candle-nn = { version = "0.10.2", features = ["cuda"] }
-candle-transformers = { version = "0.10.2", features = ["cuda"] }
+candle-core = "0.10.2"
+candle-nn = "0.10.2"
+candle-transformers = "0.10.2"
 hf-hub = { version = "0.5.0", default-features = false, features = ["ureq", "native-tls"] }
 tokenizers = "0.22.1"