Adds a full translation layer (English + European Portuguese) using
BurntSushi/toml with go:embed. Locale detection reads the lang cookie,
falls back to Accept-Language, then defaults to "en". A language switcher
in the nav writes the cookie and redirects back. All 20 personal finance
templates now use {{.T.Get "key"}} for every UI string.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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