Add auto-scroll, file dialog, and transcript editing

- Auto-scroll transcript to active segment during playback with smart
  pause when user manually scrolls (resumes after 3s)
- Replace prompt() with native Tauri file dialog for audio/video import
  with file type filters
- Add inline transcript editing via double-click with Enter to save,
  Esc to cancel, preserving original text for change tracking
- Show "edited" badge on modified segments

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

src-tauri/Cargo.lock

@@ -712,6 +712,8 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1e0e367e4e7da84520dedcac1901e4da967309406d1e51017ae1abfb97adbd38"
 dependencies = [
  "bitflags 2.11.0",
+ "block2",
+ "libc",
  "objc2",
 ]
 
@@ -2983,6 +2985,30 @@ dependencies = [
  "web-sys",
 ]
 
+[[package]]
+name = "rfd"
+version = "0.16.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a15ad77d9e70a92437d8f74c35d99b4e4691128df018833e99f90bcd36152672"
+dependencies = [
+ "block2",
+ "dispatch2",
+ "glib-sys",
+ "gobject-sys",
+ "gtk-sys",
+ "js-sys",
+ "log",
+ "objc2",
+ "objc2-app-kit",
+ "objc2-core-foundation",
+ "objc2-foundation",
+ "raw-window-handle",
+ "wasm-bindgen",
+ "wasm-bindgen-futures",
+ "web-sys",
+ "windows-sys 0.60.2",
+]
+
 [[package]]
 name = "rusqlite"
 version = "0.31.0"
@@ -3683,6 +3709,46 @@ dependencies = [
  "walkdir",
 ]
 
+[[package]]
+name = "tauri-plugin-dialog"
+version = "2.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9204b425d9be8d12aa60c2a83a289cf7d1caae40f57f336ed1155b3a5c0e359b"
+dependencies = [
+ "log",
+ "raw-window-handle",
+ "rfd",
+ "serde",
+ "serde_json",
+ "tauri",
+ "tauri-plugin",
+ "tauri-plugin-fs",
+ "thiserror 2.0.18",
+ "url",
+]
+
+[[package]]
+name = "tauri-plugin-fs"
+version = "2.4.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ed390cc669f937afeb8b28032ce837bac8ea023d975a2e207375ec05afaf1804"
+dependencies = [
+ "anyhow",
+ "dunce",
+ "glob",
+ "percent-encoding",
+ "schemars 0.8.22",
+ "serde",
+ "serde_json",
+ "serde_repr",
+ "tauri",
+ "tauri-plugin",
+ "tauri-utils",
+ "thiserror 2.0.18",
+ "toml 0.9.12+spec-1.1.0",
+ "url",
+]
+
 [[package]]
 name = "tauri-plugin-opener"
 version = "2.5.3"
@@ -4297,6 +4363,7 @@ dependencies = [
  "serde_json",
  "tauri",
  "tauri-build",
+ "tauri-plugin-dialog",
  "tauri-plugin-opener",
  "thiserror 1.0.69",
  "uuid",