Polish search and embedding UX

- add semantic text search with toolbar mode switching and sqlite-vec query support
- improve embedding progress visibility, failure recovery, and similar-image affordances
- add search clearing and keyboard controls for filename vs semantic search modes
- refine background task interactions and gallery/lightbox embedding states

Refs: #4

src-tauri/Cargo.lock

@@ -1369,6 +1369,9 @@ name = "esaxx-rs"
 version = "0.1.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d817e038c30374a4bcb22f94d0a8a0e216958d4c3dcde369b1439fec4bdda6e6"
+dependencies = [
+ "cc",
+]
 
 [[package]]
 name = "event-listener"
@@ -3962,6 +3965,7 @@ dependencies = [
  "tauri-plugin-dialog",
  "tauri-plugin-fs",
  "tauri-plugin-opener",
+ "tokenizers",
  "tokio",
  "uuid",
  "walkdir",
@@ -5944,6 +5948,7 @@ dependencies = [
  "derive_builder",
  "esaxx-rs",
  "getrandom 0.3.4",
+ "indicatif",
  "itertools",
  "log",
  "macro_rules_attribute",