release: Bump version to 1.3.1rc1

Prepare release candidate for v1.3.1 "Syndicate Tags"

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

CHANGELOG.md

@@ -7,6 +7,23 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [1.3.1] - 2025-12-10
+
+### Added
+
+- **Feed Tags/Categories** - Tags now appear in all syndication feed formats
+  - RSS 2.0: `<category>` elements for each tag
+  - Atom 1.0: `<category term="slug" label="Display Name"/>` per RFC 4287
+  - JSON Feed 1.1: `tags` array with display names
+  - Tags omitted from feeds when note has no tags
+
+### Technical Details
+
+- Enhanced: `starpunk/feeds/rss.py` with category elements
+- Enhanced: `starpunk/feeds/atom.py` with category elements
+- Enhanced: `starpunk/feeds/json_feed.py` with tags array
+- Enhanced: `starpunk/routes/public.py` pre-loads tags for feed generation
+
 ## [1.3.0] - 2025-12-10
 
 ### Added