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.

docs/brief/lifetime-licence-economics.md

@@ -1,4 +1,4 @@
-<!-- Source: Kon Master Brief — §16 Lifetime Licence Economics -->
+<!-- Source: Magnotia Master Brief — §16 Lifetime Licence Economics -->
 
 ## 16. Lifetime Licence Economics
 
@@ -6,7 +6,7 @@
 - **Affinity (Serif):** Perpetual licences (~£40/app, £135 suite) for 23 years. 53% profit margins. Acquired by Canva for ~£410M.
 - **iA Writer:** £40 Mac, £24 Windows, £16 iOS one-time. Free updates for 7+ years. Profitable with team of 12, entirely bootstrapped. Android experiment showed 50/50 split between one-time (£24) and subscription (£4/year), but purchases generated 2–3x more total revenue with significantly better retention.
 - **Sublime Text:** £79 perpetual licence with paid major-version upgrades. Sustained a tiny team for over a decade.
-- **Obsidian:** Free core + £3.20/month Sync, £6.40/month Publish. Clearest precedent for Kon's hybrid model.
+- **Obsidian:** Free core + £3.20/month Sync, £6.40/month Publish. Clearest precedent for Magnotia's hybrid model.
 
 ### Risks
 - Revenue plateaus once addressable market is saturated, while support costs continue indefinitely.