feat(database): Add Database & DBMS interactive learning module

[mnaimfaizy]

Summary

Adds a complete Database & DBMS interactive learning module to Code Executives — the 12th learning module on the platform. This module covers database fundamentals through advanced DBMS internals with 11 educational sections and 9 interactive 2D visualizations.

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New Sections

#	Section	Description
1	Introduction	Module overview, learning roadmap, and database landscape
2	Database Models	Relational, hierarchical, network, and object-oriented models
3	DBMS Architecture	Layered engine internals — process models, memory architecture
4	Query Processor	Parser, optimizer (cost model, join algorithms), cardinality estimation, plan caching
5	Storage Engine	Data page format, buffer manager, concurrency control (2PL/MVCC/OCC), ARIES recovery
6	SQL Fundamentals	DDL, DML, DQL, joins, subqueries, window functions, CTEs
7	Indexing & Optimization	B-Tree, hash, GiST/GIN/BRIN indexes, EXPLAIN plan analysis
8	Transactions & ACID	Isolation levels, lock hierarchies, deadlock detection
9	Oracle vs PostgreSQL	Deep architecture comparison — memory (SGA vs shared_buffers), processes, optimizer, indexing (12 types), MVCC, security, scalability, 15-row feature matrix
10	SQL vs NoSQL vs Vector	Comprehensive paradigm comparison — 4 NoSQL families, CAP theorem, vector DB architecture (HNSW/IVF/PQ/LSH), similarity measures, RAG pipeline, decision framework
11	Visualization Hub	All 9 interactive visualizations in a tabbed explorer

New Visualizations

Visualization	What It Shows
DatabaseTaxonomy2D	Interactive database classification tree
QueryProcessor2D	Animated query lifecycle pipeline
BTreeIndex2D	Step-by-step B-Tree insert/search operations
BufferManager2D	Buffer pool with page eviction simulation
TransactionACID2D	Concurrent transaction isolation demo
MVCCComparison2D	Oracle UNDO vs PostgreSQL inline MVCC side-by-side
ERDiagramBuilder2D	Drag-and-drop entity-relationship diagram designer
SQLvsNoSQL2D	5-category database type explorer with SVG data model diagrams
VectorDatabase2D	Vector similarity search with Brute Force / HNSW / IVF algorithm modes

Infrastructure Changes

• Routing: Added /database route with lazy-loaded section routing (App.tsx)
• Navigation: Added database entries to Header.tsx, Sidebar.tsx, and moduleNavigation.ts
• Theme: Added teal/cyan/emerald color scheme to theme.ts
• Home Page: Added Database & DBMS module card
• README: Updated module listing

Technical Details

• All sections are lazy-loaded via React.lazy() for optimal bundle splitting
• Follows the established feature-based architecture (src/features/database/)
• Uses existing shared components (SectionLayout, ThemeCard, NavigationCard, CTASection, ErrorBoundary, SEO)
• 30 files changed, ~8,500 lines added
• Build passes with zero TypeScript or Vite errors

How to Test

1. npm install && npm run dev
2. Navigate to http://localhost:5173/database
3. Use sidebar or in-page navigation to explore all 11 sections
4. Interact with visualizations (click nodes, toggle algorithms, step through animations)