Strip whitespace from comma-separated environment variables in Django settings

[Copilot]

ALLOWED_HOSTS was using .split(',') without trimming whitespace, causing Django to reject entries like ' localhost' when .env files contain spaces around commas.

Changes

• Updated ALLOWED_HOSTS to strip whitespace and filter empty strings, matching the existing CORS_ALLOWED_ORIGINS pattern
• Uses generator expression to avoid redundant strip() calls

# Before
ALLOWED_HOSTS = os.getenv("DJANGO_ALLOWED_HOSTS", "localhost,127.0.0.1").split(",")

# After
ALLOWED_HOSTS = [
    host
    for host in (
        h.strip() for h in os.getenv("DJANGO_ALLOWED_HOSTS", "localhost,127.0.0.1").split(",")
    )
    if host
]

Handles common .env formatting: DJANGO_ALLOWED_HOSTS="localhost, 127.0.0.1, 0.0.0.0" now parses correctly.

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