docs: update FEATURES.md, DEPLOYMENT.md, and CLAUDE.md

- FEATURES.md: add rich text editor section (Tiptap, formatting toolbar,
  raw markdown mode) and expand text formatting list
- DEPLOYMENT.md: fix docker-compose example to use image from ghcr.io
  instead of local build
- CLAUDE.md: add documentation maintenance instructions, update CI/CD
  section to reflect consolidated bump.yml workflow

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/FEATURES.md

@@ -8,16 +8,27 @@
 - Content supports full Markdown syntax
 - Auto-save on editor close
 
-### Markdown Support
-- **Bold** (`**text**`)
-- *Italic* (`*text*`)
+### Rich Text Editor
+- WYSIWYG editing powered by Tiptap
+- Formatting toolbar with visual controls
+- Raw Markdown mode toggle for direct editing
+- Undo/Redo with keyboard shortcuts
+
+### Text Formatting
+- **Bold** (`**text**` / Ctrl+B)
+- *Italic* (`*text*` / Ctrl+I)
+- Underline (Ctrl+U)
+- ~~Strikethrough~~ (`~~text~~` / Ctrl+Shift+X)
 - Headings (`# H1` through `###### H6`)
+- Blockquotes (`> quote`)
 - Unordered lists (`- item`)
 - Ordered lists (`1. item`)
 - Code blocks (triple backtick)
 - Inline code (single backtick)
 - Tables
-- Links (auto-linkified URLs)
+- Links — insert, edit, and remove with URL input
+- Dividers (horizontal rules)
+- Text alignment (left, center, right, justify)
 - Line breaks
 
 ### Checklists / Task Lists