Phase 4: Drop legacy entity tables

[JAORMX]

Summary

This completes the migration to the unified entity model by removing the deprecated repositories, artifacts, and pull_requests database tables.

This is Phase 4 (the final phase) of the legacy table removal plan. Phases 1-3 have already been completed:

• Phase 1: Stopped writing to legacy tables ✅
• Phase 2: Migrated all reads to entity_instances ✅
• Phase 3: Removed legacy columns from evaluation_rule_entities ✅
• Phase 4: Drop legacy tables 👈 This PR

Changes

Database Migration

• ✅ Add migration 000114 to drop legacy tables (repositories, artifacts, pull_requests)
• ✅ All data now stored in entity_instances and properties tables
• ⚠️ Down migration recreates empty tables only (data recovery requires backup restore)

Code Cleanup

• ✅ Remove SQL query files: repositories.sql, artifacts.sql
• ✅ Remove generated code: repositories.sql.go, artifacts.sql.go
• ✅ Remove db.Repository, db.Artifact, db.PullRequest structs from models
• ✅ Remove legacy methods from querier and mocks
• ✅ Remove PBRepositoryFromDB converter (internal/repositories/db.go)

Reminder Service Improvement

• ✅ Document stateless throttling approach using evaluation history
• ✅ No longer tracks reminder_last_sent timestamp in database
• ✅ Enables horizontal scaling and improves reliability
• ✅ Throttling based on MinElapsed check against actual evaluation times

Why this is better: The reminder service is now stateless and can scale horizontally. Instead of tracking "when did we last send a reminder", we check "when was this repository last evaluated". This is more reliable and eliminates unnecessary database writes.

Test Updates

• ✅ Create EntityRepository test helper for entity-based repository tests
• ✅ Update all test files to use EntityRepository instead of db.Repository
• ✅ Remove legacy repositories_test.go
• ✅ Update mock fixtures to remove legacy struct parameters
• ✅ All tests passing with full race detection ✅

Test Plan

• All unit tests pass: go test -race ./...
• All packages build: make build
• Code generation verified: make gen
• No references to legacy tables in codebase

Migration Path

1. ✅ Deploy this code to staging/production
2. ⚠️ CRITICAL: Create database backup (migration is irreversible!)
3. ✅ Run migration to drop legacy tables
4. ✅ Monitor for errors
5. ⚙️ Optional: Run VACUUM to reclaim disk space

Risk Assessment

Risk Level: HIGH (irreversible table drops)

Mitigation:

• All read/write operations already migrated to entity model in previous phases
• Code has been running in production without using legacy tables
• Down migration recreates table structure (but not data)
• Database backup required before running migration

Stats

• 22 files changed
• 252 insertions(+), 797 deletions(-) 🎉
• Net reduction: -545 lines of code

🤖 Generated with Claude Code

[coveralls]

coverage: 58.01% (+0.04%) from 57.972%
when pulling 5060e20 on JAORMX:phase4-drop-legacy-tables
into 1b9742c on mindersec:main.