chore: rename app from Solitaire Quest to Ferrous Solitaire

Replace all display-name occurrences across web pages, Rust source,
docs, and Cargo metadata. Update localStorage token key from sq_token
to fs_token. Tagline "Klondike Solitaire" retained as genre descriptor.

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

CREDITS.md

@@ -1,6 +1,6 @@
 # Credits
 
-Solitaire Quest is MIT-licensed (see [LICENSE](LICENSE)). It is built on top of
+Ferrous Solitaire is MIT-licensed (see [LICENSE](LICENSE)). It is built on top of
 the work of many open-source projects and a small handful of third-party
 assets. This file lists every component that ships in the binary or in the
 `assets/` directory.
@@ -43,7 +43,7 @@ copyleft code is statically linked into the game binary.
 | File(s) | Source | License |
 |---|---|---|
 | `solitaire_engine/assets/themes/default/{suit}_{rank}.svg` (52 SVGs) | [hayeah/playing-cards-assets](https://github.com/hayeah/playing-cards-assets) | MIT |
-| `solitaire_engine/assets/themes/default/back.svg` | Original — Solitaire Quest | MIT (this project) |
+| `solitaire_engine/assets/themes/default/back.svg` | Original — Ferrous Solitaire | MIT (this project) |
 | `assets/cards/faces/{RANK}{SUIT}.png` (52 PNGs) | Pre-rendered from the same `playing-cards-assets` SVGs | MIT (passed through from hayeah) |
 | `assets/cards/backs/back_0.png` – `back_4.png` | Original — generated by `solitaire_assetgen::gen_art` | MIT (this project) |
 
@@ -107,6 +107,6 @@ Audio files are MIT-licensed alongside the rest of this project.
   backs, every audio file) are original work covered by this project's MIT
   license.
 
-If you redistribute Solitaire Quest, you must ship this `CREDITS.md` and the
+If you redistribute Ferrous Solitaire, you must ship this `CREDITS.md` and the
 `LICENSE` file alongside the binary so the MIT (project + hayeah card art)
 and OFL (FiraMono) notices remain visible to end users.