fix(setup): reduce friction in installation procedure

- Add Language default ("jp") so missing field no longer produces empty
  string, and include language selector in setup wizard
- Add --setup flag to re-run wizard even when config.json exists,
  providing a recovery path for corrupted configs
- Auto-apply seed data on fresh databases so users who skip the wizard
  still get shops, events, and gacha
- Fix stale docs referencing non-existent init/setup.sh and
  schemas/patch-schema/ in docker/README, CONTRIBUTING, and README

server/setup/wizard.go

@@ -26,6 +26,7 @@ type FinishRequest struct {
 	DBPassword        string `json:"dbPassword"`
 	DBName            string `json:"dbName"`
 	Host              string `json:"host"`
+	Language          string `json:"language"`
 	ClientMode        string `json:"clientMode"`
 	AutoCreateAccount bool   `json:"autoCreateAccount"`
 }
@@ -33,8 +34,13 @@ type FinishRequest struct {
 // buildDefaultConfig produces a minimal config map with only user-provided values.
 // All other settings are filled by Viper's registered defaults at load time.
 func buildDefaultConfig(req FinishRequest) map[string]interface{} {
+	lang := req.Language
+	if lang == "" {
+		lang = "jp"
+	}
 	return map[string]interface{}{
 		"Host":              req.Host,
+		"Language":          lang,
 		"ClientMode":        req.ClientMode,
 		"AutoCreateAccount": req.AutoCreateAccount,
 		"Database": map[string]interface{}{

server/setup/wizard.html

@@ -145,10 +145,20 @@ h1{font-size:1.75rem;margin-bottom:.5rem;color:#e94560;text-align:center}
     </div>
     <div style="font-size:.75rem;color:#666;margin-top:.3rem">Use 127.0.0.1 for local play, or auto-detect for LAN/internet play.</div>
   </div>
-  <div class="field">
-    <label>Client Mode</label>
-    <select id="srv-client-mode"></select>
-    <div style="font-size:.75rem;color:#666;margin-top:.3rem">Must match your game client version. ZZ is the latest.</div>
+  <div class="field-row">
+    <div class="field">
+      <label>Client Mode</label>
+      <select id="srv-client-mode"></select>
+      <div style="font-size:.75rem;color:#666;margin-top:.3rem">Must match your game client version. ZZ is the latest.</div>
+    </div>
+    <div class="field field-sm">
+      <label>Language</label>
+      <select id="srv-language">
+        <option value="jp" selected>jp</option>
+        <option value="en">en</option>
+      </select>
+      <div style="font-size:.75rem;color:#666;margin-top:.3rem">Game text language.</div>
+    </div>
   </div>
   <label class="checkbox" style="margin-top:1rem"><input type="checkbox" id="srv-auto-create" checked> Auto-create accounts (recommended for private servers)</label>
   <div class="actions">
@@ -339,6 +349,7 @@ function buildReview() {
     ['Database Password', masked],
     ['Database Name', document.getElementById('db-name').value],
     ['Server Host', document.getElementById('srv-host').value],
+    ['Language', document.getElementById('srv-language').value],
     ['Client Mode', document.getElementById('srv-client-mode').value],
     ['Auto-create Accounts', document.getElementById('srv-auto-create').checked ? 'Yes' : 'No'],
   ];
@@ -362,6 +373,7 @@ async function finish() {
         dbPassword: document.getElementById('db-password').value,
         dbName: document.getElementById('db-name').value,
         host: document.getElementById('srv-host').value,
+        language: document.getElementById('srv-language').value,
         clientMode: document.getElementById('srv-client-mode').value,
         autoCreateAccount: document.getElementById('srv-auto-create').checked,
       })