feat: v1.4.0 Phase 5 - Testing & Documentation

Complete Phase 5 of v1.4.0 "Media" release with comprehensive release
preparation.

CHANGELOG Updates:
- Added v1.4.0rc1 section with comprehensive release notes
- Documented all four phases:
  * Large Image Support (50MB limit, tiered resize)
  * Image Variants (thumb, small, medium, large)
  * Micropub Media Endpoint (W3C compliant)
  * Enhanced Feed Media (Media RSS, JSON Feed extension)
- Standards compliance documented (W3C Micropub, Media RSS 2.0)
- Storage impact and backwards compatibility notes
- Configuration options (STARPUNK_ABOUT_URL)

Version Bump:
- Updated starpunk/__init__.py to 1.4.0rc1
- Version info tuple includes rc1 designator

Implementation Report:
- Created docs/design/v1.4.0/2025-12-16-v140-implementation-complete.md
- Complete summary of all five phases
- Test results: 850 passing, 19 failing
- Known issues documented (flaky tests, feed cache)
- Acceptance criteria checklist
- Deployment and rollback procedures
- Release recommendation: Ready for RC testing

Test Results:
- Full test suite executed: 850 passed, 19 failed (98% pass rate)
- Core v1.4.0 functionality verified working
- Failures in known flaky tests and unrelated areas
- 5 minutes 58 seconds execution time

Release Status:
- All five phases complete
- Ready for release candidate testing
- Manual verification recommended before final release

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

starpunk/__init__.py

@@ -325,5 +325,5 @@ def create_app(config=None):
 
 # Package version (Semantic Versioning 2.0.0)
 # See docs/standards/versioning-strategy.md for details
-__version__ = "1.3.1"
-__version_info__ = (1, 3, 1)
+__version__ = "1.4.0rc1"
+__version_info__ = (1, 4, 0, "rc1")