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.

crates/transcription/tests/whisper_rs_smoke.rs

@@ -1,17 +1,17 @@
 //! Smoke test: whisper-rs 0.16 loads a GGUF model, transcribes silence, and
 //! accepts set_initial_prompt without panicking.
 //!
-//! Runs only when `KON_WHISPER_TEST_MODEL` is set to the path of a
+//! Runs only when `MAGNOTIA_WHISPER_TEST_MODEL` is set to the path of a
 //! ggml/gguf whisper model on disk. Otherwise the test exits quiet.
 
 use std::env;
 
 #[test]
 fn whisper_rs_smoke_loads_and_transcribes() {
-    let model_path = match env::var("KON_WHISPER_TEST_MODEL") {
+    let model_path = match env::var("MAGNOTIA_WHISPER_TEST_MODEL") {
         Ok(p) => p,
         Err(_) => {
-            eprintln!("KON_WHISPER_TEST_MODEL not set — skipping");
+            eprintln!("MAGNOTIA_WHISPER_TEST_MODEL not set — skipping");
             return;
         }
     };