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/community-plugins.json

@@ -1,3 +1,10 @@
 [
-  "obsidian-git"
-]
+  "obsidian-git",
+  "dataview",
+  "kanban",
+  "calendar",
+  "heatmap",
+  "obsidian-tasks-plugin",
+  "obsidian-chart",
+  "obsidian-advanced-slides"
+]