Fix backend infrastructure issues: Redis consolidation, migration mis…

[0xdevmes]

Fix Backend Infrastructure Issues

This PR addresses four critical infrastructure issues in the Web3-Student-Lab backend to improve resource management, database consistency, and concurrency safety.

Changes Made

#994 - Consolidate dual Redis connection managers

• Modified RedisClient.ts to include pubClient and subClient properties with dedicated getter methods (getPubClient(), getSubClient(), getBullMQClient())
• Refactored utils/redis.ts to re-export clients from the centralized RedisClient singleton, eliminating duplicate connection instances
• Updated all 20+ files previously importing from utils/redis.ts to use the centralized redisClient via getter methods
• This eliminates resource waste and enables proper caching by ensuring all Redis operations use a single connection manager

#999 - Fix SQLite vs PostgreSQL migration mismatch

• Fixed migration_lock.toml to use postgresql provider instead of sqlite
• Removed the SQLite dev.db file that was causing confusion between local development and production database configurations
• Ensures Prisma migrations correctly target PostgreSQL in all environments

#988 - Complete read-replica database routing implementation

• Read-replica routing middleware was already implemented in db/index.ts and requestContext.ts with proper context-aware routing
• Added db-read-replica service to docker-compose.yml for local development and testing
• Added DB_READ_REPLICA_URL environment variable to backend service configuration
• Added read replica health check dependency to backend service
• Enables read operations to be routed to read replicas for improved performance and scalability

#991 - Add pessimistic locking for wallet creation endpoints

• Added pessimistic locking to the register function in auth/auth.service.ts
• Used Prisma transaction with Serializable isolation level to prevent race conditions
• Prevents concurrent registration attempts from assigning the same wallet address to multiple users
• Ensures data integrity during wallet address assignment

Files Modified

• 23 files changed, 276 insertions(+), 214 deletions(-)
• Key files: RedisClient.ts, utils/redis.ts, auth.service.ts, migration_lock.toml, docker-compose.yml, and all Redis client imports across the codebase

Testing Recommendations

• Test Redis pub/sub functionality with the new centralized client
• Verify database migrations run correctly with the fixed migration lock
• Test read-replica routing with the new docker-compose service
• Test concurrent registration attempts to verify pessimistic locking works

Closes #994
Closes #999
Closes #988
Closes #991

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[ayomideadeniran]

Pr under review.

[ayomideadeniran]

Pr under review.