feat(web): sign-in, first-run setup, app shell and user admin (M1)

- core: AuthSession keeps the access token in memory, refreshes it
  once for all parallel requests (single-flight) and retries them;
  refresh races between tabs are retried, reuse signs out; ApiError
  carries problem+json codes and field errors
- web: TanStack Router with guards — guests go to /login, the bootstrap
  admin to /setup/admin, temporary passwords to /setup/password, admin
  pages by role
- login, setup screens, Classic shell (top bar, role-based sidebar,
  empty player), settings: name, theme, language, password, devices
- users admin: search, role filter, create with a one-time temporary
  password, reset, block, role change, delete as the policy allows;
  audit log for admins
- ru/en strings for auth, admin and error codes; language and theme
  are saved in the profile

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/i18n/locales/en/admin.json

@@ -0,0 +1,66 @@
+{
+  "users": {
+    "title": "Users",
+    "subtitle": "Create users and moderators, manage roles, reset passwords, block accounts",
+    "create": "Create user",
+    "search": "Name or username",
+    "all": "All",
+    "col_user": "User",
+    "col_role": "Role",
+    "col_status": "Status",
+    "col_last_login": "Last seen",
+    "status_active": "Active",
+    "status_blocked": "Blocked",
+    "status_must_change": "Must change password",
+    "never": "Never signed in",
+    "empty": "Nobody found",
+    "more": "Show more",
+    "actions": "Actions for {{username}}",
+    "reset_password": "Reset password",
+    "block": "Block",
+    "unblock": "Unblock",
+    "make_role": "Make {{role}}",
+    "delete": "Delete",
+    "delete_confirm": "Delete {{username}}? Their history and likes will be lost.",
+    "block_confirm": "Block {{username}}? All their sessions will end.",
+    "reset_confirm": "Reset {{username}}'s password? All their sessions will end.",
+    "confirm": "Confirm",
+    "you": "you"
+  },
+  "create": {
+    "title": "New user",
+    "username": "Username",
+    "username_hint": "Latin letters, digits, \".\", \"_\", \"-\"",
+    "display_name": "Name",
+    "role": "Role",
+    "password_note": "The server will generate a password and show it once.",
+    "submit": "Create"
+  },
+  "temp_password": {
+    "title": "Temporary password",
+    "text": "Give this password to {{username}}. It is shown only now; they will be asked to change it on sign-in.",
+    "done": "Done"
+  },
+  "audit": {
+    "title": "Audit log",
+    "subtitle": "Actions of administrators and moderators",
+    "col_when": "When",
+    "col_who": "Who",
+    "col_action": "Action",
+    "col_details": "Details",
+    "system": "System",
+    "empty": "No entries yet",
+    "more": "Show more",
+    "actions": {
+      "user.bootstrap_create": "Initial administrator created",
+      "user.bootstrap_credentials": "Administrator credentials set",
+      "user.create": "User created",
+      "user.rename": "Name changed",
+      "user.role_change": "Role changed",
+      "user.block": "User blocked",
+      "user.unblock": "User unblocked",
+      "user.password_reset": "Password reset",
+      "user.delete": "User deleted"
+    }
+  }
+}

packages/i18n/locales/en/auth.json

@@ -0,0 +1,24 @@
+{
+  "login": {
+    "title": "Sign in",
+    "subtitle": "Your music from your own server",
+    "username": "Username",
+    "password": "Password",
+    "submit": "Sign in",
+    "bootstrap_hint": "First start: sign in as the administrator. The password is set in BOOTSTRAP_ADMIN_PASSWORD or printed in the api service log."
+  },
+  "setup": {
+    "admin_badge": "First administrator sign-in",
+    "admin_title": "Change the username and password",
+    "admin_text": "The server stays locked until you do: the initial administrator credentials are visible in logs and settings.",
+    "password_badge": "Password reset",
+    "password_title": "Set a new password",
+    "password_text": "You signed in with a temporary password. Choose your own — the temporary one will stop working.",
+    "new_username": "New username",
+    "new_password": "New password",
+    "repeat_password": "Repeat the password",
+    "min_length": "At least {{min}} characters",
+    "submit": "Save and continue",
+    "logout": "Sign out"
+  }
+}

packages/i18n/locales/en/common.json

@@ -17,5 +17,67 @@
     "label": "Language",
     "ru": "Русский",
     "en": "English"
+  },
+  "nav": {
+    "main": "Navigation",
+    "home": "Home",
+    "admin": "Admin",
+    "users": "Users",
+    "audit": "Audit log"
+  },
+  "profile": {
+    "menu": "Profile menu",
+    "settings": "Settings",
+    "logout": "Sign out"
+  },
+  "roles": {
+    "admin": "Administrator",
+    "moderator": "Moderator",
+    "user": "User"
+  },
+  "home": {
+    "greeting": "Hi, {{name}}!",
+    "wave": "My Wave",
+    "wave_soon": "An endless stream tuned to your taste will appear once the server has a library."
+  },
+  "player": {
+    "empty": "Nothing is playing"
+  },
+  "settings": {
+    "title": "Settings",
+    "account": "Account",
+    "display_name": "Display name",
+    "save": "Save",
+    "saved": "Saved",
+    "appearance": "Appearance",
+    "theme": "Theme",
+    "theme_dark": "Dark",
+    "theme_light": "Light",
+    "theme_system": "System",
+    "password": "Password",
+    "current_password": "Current password",
+    "new_password": "New password",
+    "repeat_password": "Repeat the password",
+    "change_password": "Change password",
+    "password_changed": "Password changed. Other devices have been signed out.",
+    "sessions": "Devices",
+    "session_current": "This device",
+    "session_last_used": "Active: {{date}}",
+    "session_end": "Sign out",
+    "logout_all": "Sign out everywhere"
+  },
+  "form": {
+    "show_password": "Show password",
+    "hide_password": "Hide password",
+    "passwords_mismatch": "Passwords don't match",
+    "required": "Fill in this field",
+    "cancel": "Cancel",
+    "close": "Close",
+    "copy": "Copy",
+    "copied": "Copied"
+  },
+  "loading": "Loading…",
+  "route_error": {
+    "reload": "Reload the page"
   }
 }

packages/i18n/locales/en/errors.json

@@ -3,7 +3,8 @@
     "internal": "Something went wrong on the server. Please try again",
     "bad_request": "Invalid request",
     "not_found": "Not found",
-    "method_not_allowed": "This action is not supported"
+    "method_not_allowed": "This action is not supported",
+    "network": "Cannot reach the server. Check your network"
   },
   "auth": {
     "invalid_credentials": "Wrong username or password",