feat: add Obsidian visualization plugins and guide

Added comprehensive visualization plugins and setup guide:

**Installed Community Plugins:**
1. **Dataview** - Query and visualize data from Markdown files
   - Create tables, lists, task views
   - Filter and sort by metadata
2. **Kanban** - Task board with drag-and-drop
   - Track learning progress
   - Manage interview prep tasks
3. **Calendar** - Daily notes with calendar view
   - Track study consistency
   - Auto-generate daily journals
4. **Heatmap** - Activity heatmap (GitHub-style)
   - Visualize study frequency
   - Track learning streaks
5. **Obsidian Tasks** - Advanced task management
   - Query tasks by due date, tags, priority
   - Track overdue and upcoming tasks
6. **Obsidian Chart** - Create charts and graphs
   - Pie charts, bar charts, line charts
   - Visualize learning statistics
7. **Advanced Slides** - Create presentations
   - Build interview prep slides
   - Support for Marp.js

**Enhanced Core Plugins:**
- Enabled Graph Analysis for better relationship visualization
- Enabled Webviewer for embedded content

**Created Documentation:**
- Comprehensive installation and usage guide
- Plugin configuration examples
- Best practices for interview preparation
- Keyboard shortcuts
- Troubleshooting tips

**Use Cases:**
- Build knowledge graph with Graph View + Canvas
- Track progress with Calendar + Heatmap + Tasks
- Review problems with Dataview + Kanban
- Create presentations with Advanced Slides

All configurations saved in .obsidian/ directory for automatic sync.

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

.obsidian/core-plugins.json

@@ -3,31 +3,23 @@
   "global-search": true,
   "switcher": true,
   "graph": true,
+  "graph-analysis": true,
   "backlink": true,
   "canvas": true,
   "outgoing-link": true,
   "tag-pane": true,
-  "footnotes": false,
   "properties": true,
   "page-preview": true,
   "daily-notes": true,
   "templates": true,
   "note-composer": true,
   "command-palette": true,
-  "slash-command": false,
   "editor-status": true,
   "bookmarks": true,
-  "markdown-importer": false,
-  "zk-prefixer": false,
-  "random-note": false,
   "outline": true,
   "word-count": true,
-  "slides": false,
-  "audio-recorder": false,
-  "workspaces": false,
   "file-recovery": true,
-  "publish": false,
   "sync": true,
   "bases": true,
-  "webviewer": false
-}
+  "webviewer": true
+}