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/core/src/lib.rs

@@ -7,7 +7,7 @@ pub mod process_watch;
 pub mod recommendation;
 pub mod types;
 
-pub use error::{KonError, Result};
+pub use error::{MagnotiaError, Result};
 pub use types::{
     AudioSamples, DownloadProgress, EngineName, Megabytes, ModelId, Segment, Transcript,
     TranscriptionOptions,