PostGIS Extension Not Available After Multiple Compute Restarts

-- Check for PostGIS in available extensions
SELECT * FROM pg_available_extensions WHERE name LIKE '%postgis%';
-- Result: (0 rows)

-- Attempt to create PostGIS extension
CREATE EXTENSION IF NOT EXISTS postgis;
-- Error: extension "postgis" is not available
-- HINT: The extension must first be installed on the system where PostgreSQL is running.

-- Check all spatial/geo-related extensions
SELECT name, default_version, comment FROM pg_available_extensions 
WHERE name ~ '.*(geo|spatial|gis|geom).*' ORDER BY name;
-- Result: Only btree_gist (1.8) - support for indexing common datatypes in GiST