Look up an Icelandic word form and return all matching entries from BÍN.

This finds all possible interpretations of a word form, including its
lemma(s), word class(es), and grammatical tags.

Args:
    word: The Icelandic word form to look up (e.g., "hestur", "færi", "hestana")
    at_sentence_start: If True, also check lowercase forms when the word
        is capitalized (useful for words at the start of sentences)

Returns:
    A dict with:
    - found: Whether any matches were found
    - search_key: The actual search key used (may differ if z->s replacement occurred)
    - entries: List of matching entries, each with lemma, word_class, domain,
      inflection_form, and grammatical_tag

Get a specific grammatical variant of an Icelandic word.

This converts a word to a different case, number, person, tense, etc.
For example, convert "hestur" to dative plural, or "fallegur" to superlative.

Args:
    word: The base word to convert (e.g., "hestur", "fallegur", "fara")
    word_class: The word class to disambiguate the word. Common values:
        - "kk" (masculine noun), "kvk" (feminine noun), "hk" (neutral noun)
        - "no" (any noun)
        - "so" (verb)
        - "lo" (adjective)
    target_form: List of grammatical feature tags to request. Examples:
        - ["ÞGF"] - dative case
        - ["ÞGF", "FT"] - dative plural
        - ["NF", "FT", "gr"] - nominative plural with definite article
        - ["nogr"] - indefinite form (no article)
        - ["EVB", "KVK"] - superlative weak form, feminine
        - ["FH", "NT", "3P"] - indicative, present tense, 3rd person

Returns:
    A dict with:
    - variants: List of matching variants, each with inflection_form,
      grammatical_tag, and lemma

Find the lemma(s) and word class(es) for an Icelandic word form.

Given any inflected form, this returns all possible base forms (lemmas)
and their word classes.

Args:
    word: The word form to analyze (e.g., "hestana", "laga", "færi")

Returns:
    A dict with:
    - lemmas: List of possible lemmas, each with lemma and word_class