List Sanatan Dharma festivals computed for any city/range.

Each festival is returned with:

• Gregorian date (local timezone)
• Bilingual name (en + hi)
• Deity, description, lane classification
• Muhurat windows (Pradosh, Nishita, Abhijit, Bhadra-avoid)
• Rule explanation (which tithi/nakshatra/sankranti instant drives the date)

Math: tithi = (Moon longitude - Sun longitude) / 12° · sidereal standard-frame reference frame. See app/festivals.py for the full algorithm.

Transport: the response is gzip-compressed when the client advertises Accept-Encoding: gzip and the body clears the size threshold; the decompressed body is byte-identical to the plain JSON, and identity clients are unchanged. The payload is computed by _panchang_festivals_dict, which /panchang/month also calls internally (consuming the dict directly, so it is unaffected by the route's transport encoding).