chore: rename app from Solitaire Quest to Ferrous Solitaire

Updates all in-tree references:
- Android package: com.solitairequest.app → com.ferrousapp.solitaire
- APK name: solitaire-quest → ferrous-solitaire
- Data dir: solitaire_quest → ferrous_solitaire (across all 6 data modules + engine)
- Keyring service: solitaire_quest_server → ferrous_solitaire_server
- Android Keystore key: solitaire_quest_token_key → ferrous_solitaire_token_key
- Gitea repo: Rusty_Solitare → Ferrous-Solitaire (also fixes "Solitare" typo)
- Renamed pkg/solitaire-quest* → pkg/ferrous-solitaire*
- Updated ArgoCD, docker-compose, CI workflow, build script, all docs

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

pkg/ferrous-solitaire-server/server.env

@@ -0,0 +1,15 @@
+# Ferrous Solitaire Server — environment configuration
+# This file is installed to /etc/ferrous-solitaire-server/server.env (mode 0640).
+# Edit these values before starting the service.
+
+# Path to the SQLite database file.
+# The directory must be writable by the ferrous-solitaire service user.
+DATABASE_URL=sqlite:///var/lib/ferrous-solitaire-server/solitaire.db
+
+# HS256 signing secret for JWT tokens.
+# Generate a strong secret with: openssl rand -hex 32
+# REQUIRED — server will refuse to start if unset.
+JWT_SECRET=changeme_generate_with_openssl_rand_hex_32
+
+# TCP port the server listens on.
+SERVER_PORT=8080