# Implementation Plan: Issue #192 — Database Portability

## Summary
Replace 5 MySQL-specific SQL expressions with platform-aware equivalents using a new PlatformHelper utility class, declare PostgreSQL and SQLite support in info.xml, add Docker infrastructure for all three backends, create integration tests, and set up CI pipeline.

## Phase 1: Core Portability Fixes
1. Create `lib/Db/PlatformHelper.php` with 3 methods:
   - `getYearDiffExpression($db, $col)` — age/duration calculation
   - `getMonthExpression($db, $col)` — extract month
   - `getYearExpression($db, $col)` — extract year
2. Update `lib/Service/QueryService.php` lines 300, 318 — use PlatformHelper
3. Update `lib/Db/MemberMapper.php` lines 165, 301 — use PlatformHelper
4. Update `lib/Db/LagerMapper.php` line 70 — use PlatformHelper
5. Update `appinfo/info.xml` — add pgsql and sqlite database declarations

## Phase 2: Docker Infrastructure
6. Create `docker/postgres/docker-compose.yml`
7. Create `docker/sqlite/docker-compose.yml`
8. Add Makefile targets for postgres and sqlite

## Phase 3: Integration Tests
9. Create `tests/DatabasePortability/PlatformHelperTest.php`

## Phase 4: CI Pipeline
10. Create `.gitea/workflows/database-portability.yml`

## Phase 5: Security Review
11. Verify PlatformHelper introduces no SQL injection vectors
12. Verify column expressions are hardcoded, not user-supplied

## AC Verification Checklist
1. [ ] appinfo/info.xml declares mysql, pgsql, and sqlite
2. [ ] No MySQL-specific SQL remains (no TIMESTAMPDIFF, CURDATE, LIKE on date columns)
3. [ ] PlatformHelper generates correct expressions for all 3 backends
4. [ ] Age/duration filters use PlatformHelper
5. [ ] Birthday-this-month filter uses PlatformHelper
6. [ ] Lager findByYear uses PlatformHelper
7. [ ] Docker Compose files exist for MySQL, PostgreSQL, and SQLite
8. [ ] Integration test suite exists
9. [ ] CI pipeline definition exists
10. [ ] No SQL injection vectors introduced (all expressions use hardcoded column names)