chore: rebrand from Kon/Corbie to Magnotia

Replace all instances of the legacy product names "Kon" and "Corbie" with
"Magnotia" across user-facing copy, code identifiers, package names, bundle
ids, file paths, and documentation. Preserves the unrelated "konsole" (KDE
terminal) reference and the parent CORBEL company name.

- Renames 10 Rust crates (kon-* → magnotia-*) and the tauri binary
- Updates package.json, tauri.conf.json (productName + identifier)
- Renames CSS classes (kon-rh-* → magnotia-rh-*) and animations
- Renames brand and roadmap docs
- Regenerates Cargo.lock and package-lock.json

Verified: svelte-check passes; pure-rust crates compile under new names.

src-tauri/src/commands/windows.rs

@@ -60,7 +60,7 @@ pub async fn open_task_window(app: tauri::AppHandle) -> Result<(), String> {
 
     let mut builder =
         WebviewWindowBuilder::new(&app, "tasks-float", WebviewUrl::App("/float".into()))
-            .title("Kon Tasks")
+            .title("Magnotia Tasks")
             .inner_size(480.0, 520.0)
             .min_inner_size(360.0, 480.0)
             .always_on_top(true)
@@ -113,7 +113,7 @@ pub async fn open_preview_window(app: tauri::AppHandle) -> Result<(), String> {
         "transcription-preview",
         WebviewUrl::App("/preview".into()),
     )
-    .title("Kon — Preview")
+    .title("Magnotia — Preview")
     .inner_size(420.0, 200.0)
     .min_inner_size(360.0, 140.0)
     .max_inner_size(520.0, 360.0)
@@ -178,7 +178,7 @@ pub async fn open_viewer_window(app: tauri::AppHandle) -> Result<(), String> {
 
     let mut builder =
         WebviewWindowBuilder::new(&app, "transcript-viewer", WebviewUrl::App("/viewer".into()))
-            .title("Kon - Transcription Editor")
+            .title("Magnotia - Transcription Editor")
             .inner_size(600.0, 700.0)
             .min_inner_size(560.0, 520.0)
             .decorations(use_native_decorations)