feat: v1.4.0 Phase 3 - Micropub Media Endpoint

Implement W3C Micropub media endpoint for external client uploads.

Changes:
- Add POST /micropub/media endpoint in routes/micropub.py
  - Accept multipart/form-data with 'file' field
  - Require bearer token with 'create' scope
  - Return 201 Created with Location header
  - Validate, optimize, and generate variants via save_media()

- Update q=config response to advertise media-endpoint
  - Include media-endpoint URL in config response
  - Add 'photo' post-type to supported types

- Add photo property support to Micropub create
  - extract_photos() function to parse photo property
  - Handles both simple URL strings and structured objects with alt text
  - _attach_photos_to_note() function to attach photos by URL
  - Only attach photos from our server (by URL match)
  - External URLs logged but ignored (no download)
  - Maximum 4 photos per note (per ADR-057)

- SITE_URL normalization pattern
  - Use .rstrip('/') for consistent URL comparison
  - Applied in media endpoint and photo attachment

Per design document: docs/design/v1.4.0/media-implementation-design.md

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

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

docs/projectplan/BACKLOG.md

@@ -36,10 +36,25 @@
 - ATOM enclosure links for all media
 - See: ADR-059
 
+### POSSE 
+- Native syndication to social networks
+- Supported networks:
+  - First iteration: 
+    - Mastodon (and compatible services)
+    - Bluesky
+  - Second iteration 
+    - TBD 
+- Solution should include a configuration UI for setup
+
 ---
 
 ## Medium
 
+### Default slug change 
+- The default slug should be a date time stamp 
+- YYYYMMDDHHMMSS
+- Edge case, if the slug would somehow be a duplicate append a "-x" e.g. -1 
+
 ### Tag Enhancements (v1.3.0 Follow-up)
 - Tag pagination on archive pages (when note count exceeds threshold)
 - Tag autocomplete in admin interface