Adds unit tests for feed module and integration tests for feed route.
test_feed.py:
- Feed generation with various note counts
- RFC-822 date formatting
- Note title extraction
- HTML cleaning for CDATA safety
- Feed structure validation
- Special characters and Unicode handling
test_routes_feed.py:
- Feed route accessibility and response
- Content-Type and cache headers
- ETag generation and validation
- Server-side caching behavior
- Published notes filtering
- Feed item limit configuration
- Configuration integration
All tests follow existing test patterns and use proper fixtures.
Phil Skentelbery
9a31632e05