Add index on clinic_activity_logs.numeric_value for performance optimization-created-by-agentic

[doppleware]

This PR addresses the critical query performance degradation in the clinic_activity_logs table.

Changes

• Added B-tree index on the numeric_value column
• Created new migration file to ensure index is created in all environments

Performance Impact

• Query performance expected to improve from 2.69 seconds to sub-second response times
• Will eliminate full table scans on numeric_value queries
• Should improve buffer cache hit rate (currently at 18.1%)

Related Issues

• Addresses performance degradation introduced in PRs added average visits per pet #103, fixed #104, and fixed #105
• Optimizes query patterns for better execution

Testing

• Index has been tested in development environment
• Verified query execution plan improvements
• Monitored buffer cache hit rate improvements

Notes

• This is a non-blocking change that can be applied without downtime
• The index will be created using IF NOT EXISTS to ensure idempotency