refactor(auth): merge the duplicate login form and localize the auth screens

`home-login-form.tsx` and `login-form.tsx` were two ~240-line near-identical
components. Delete the former and give `LoginForm` a `variant` prop:

- `variant="page"`   sr-only labels plus the register/forgot footer (/login)
- `variant="compact"` visible labels, no footer (homepage sidebar)

Field ids now come from `useId()`, so the two usages can never collide, and the
hardcoded "Show"/"Hide"/"Loading" strings are translated.

Localization of the login and register screens:

- `home-login-form.tsx` was entirely hardcoded English.
- `passwordStrength()` returned hardcoded "Weak"/"Fair"/"Good"/"Strong".
- `register.ts` returned only English strings. It now returns a
  locale-independent `code` next to the message, and the form renders
  `t(code)` with the English string as a fallback.
- Backfilled the new keys across all 25 locales, plus the login/register
  strings that were still English in most of them. `ar`, `fi` and `ja` had
  their entire login/register namespace in English and are now filled in.
  Locale parity stays at 0 missing keys, as `i18n:check` requires.

Copy that did not match the enforced rules: the UI advertised "min 8 chars"
(EN) / "min 6 tekens" (NL) while registration requires 12 characters plus an
uppercase, a lowercase, a digit and a special character. Corrected in every
locale. `password-reset.ts` enforced only 6 characters and is raised to 12 to
match registration.

Accessibility: `login-form.tsx` had no `<label>`, no `id` and no `required` on
any field. All three are now present, and error banners are announced with
`role="alert"`.

Adds `src/i18n/auth-messages.test.ts`, which asserts every `RegisterErrorCode`
resolves to a non-empty message in all 25 locales; verified it fails when a key
is removed. The existing register tests now also assert the error `code`.

src/messages/en.json

@@ -1015,7 +1015,11 @@
 			"errorCaptcha": "Captcha verification failed. Please try again.",
 			"whoIsOnline": "Who's online",
 			"newestCitizens": "Newest citizens",
-			"usersOnline": "{count} online"
+			"usersOnline": "{count} online",
+			"showPassword": "Show",
+			"hidePassword": "Hide",
+			"username": "Username",
+			"password": "Password"
 		},
 		"register": {
 			"title": "Create account",
@@ -1026,7 +1030,7 @@
 			"confirmPassword": "Repeat password",
 			"usernamePlaceholder": "Username",
 			"emailPlaceholder": "Email",
-			"passwordPlaceholder": "Password (min 8 chars)",
+			"passwordPlaceholder": "Password (min 12 chars)",
 			"confirmPasswordPlaceholder": "Repeat password",
 			"selectOutfit": "Select your outfit",
 			"termsAccept": "I am 18+ and accept the {hotel} terms & rules.",
@@ -1049,14 +1053,39 @@
 			"termsError": "You must accept the terms & rules to register.",
 			"usernameError": "Username is required.",
 			"emailError": "Valid email is required.",
-			"passwordError": "Password must be at least 6 characters.",
+			"passwordError": "Password must be at least 12 characters",
 			"confirmPasswordError": "Passwords do not match.",
 			"termsRequired": "You must accept the terms & rules.",
 			"usernameRequired": "Username is required.",
 			"emailRequired": "Email is required.",
 			"passwordRequired": "Password is required.",
 			"passwordsDontMatch": "Passwords do not match.",
-			"invitedBy": "Invited by {username}"
+			"invitedBy": "Invited by {username}",
+			"strengthWeak": "Weak",
+			"strengthFair": "Fair",
+			"strengthGood": "Good",
+			"strengthStrong": "Strong",
+			"passwordMinLength": "Password must be at least 12 characters",
+			"passwordUpper": "Password must contain at least one uppercase letter",
+			"passwordLower": "Password must contain at least one lowercase letter",
+			"passwordDigit": "Password must contain at least one digit",
+			"passwordSpecial": "Password must contain at least one special character",
+			"passwordMaxLength": "Password is too long",
+			"usernameMinLength": "Username must be at least 3 characters",
+			"usernameMaxLength": "Username must be at most 25 characters",
+			"usernamePattern": "Username may only contain letters, numbers, underscore and hyphen",
+			"usernameReserved": "This username is reserved",
+			"emailValid": "Enter a valid email address",
+			"emailDisposable": "Temporary email domains are not allowed",
+			"passwordsMatch": "Passwords do not match",
+			"usernameTaken": "That username is already taken",
+			"captchaFailed": "Captcha verification failed. Please try again.",
+			"rateLimited": "Too many sign-up attempts. Please wait a few minutes and try again.",
+			"vpnBlocked": "Registrations from VPN/proxy connections are not allowed.",
+			"maxAccountsPerIp": "You have reached the maximum number of accounts for your connection.",
+			"unavailable": "Registration is temporarily unavailable.",
+			"createFailed": "Could not create the account. Please try again or contact staff.",
+			"invalidInput": "Please check the highlighted fields and try again."
 		},
 		"forgot": {
 			"title": "Reset password",
@@ -1070,9 +1099,11 @@
 		"reset": {
 			"title": "Set a new password",
 			"subtitle": "Choose a strong password you don't use elsewhere.",
-			"passwordPlaceholder": "New password (min 6 chars)",
+			"passwordPlaceholder": "New password (min 12 chars)",
 			"resetPassword": "Reset password",
-			"backToLogin": "Back to login"
+			"backToLogin": "Back to login",
+			"passwordMinLength": "Password must be at least 12 characters",
+			"tooManyAttempts": "Too many attempts — try again later"
 		},
 		"verify": {
 			"verifiedTitle": "You're all set",