docs: add testing strategy and version requirements to schema plan

- Add PostgreSQL version requirements section (min 13, rec 15)
- Add unit testing section for schema.go functions
- Add concurrent startup manual test with 5 instances
- Add debug hint in executeSchema error messages
- Add PostgreSQL troubleshooting section
- Update documentation requirements to include testing

REFINED_SCHEMA_PLAN.md

@@ -16,6 +16,17 @@
 
 ## 📊 Technical Decisions
 
+### PostgreSQL Version Requirements
+
+**Minimum: PostgreSQL 13** (for `gen_random_uuid()`)
+**Recommended: PostgreSQL 15** (matches `docker-compose.yml`)
+**IF NOT EXISTS syntax:** PostgreSQL 9.5+ (already satisfied by minimum version)
+
+**Rationale:**
+- PostgreSQL 13 introduced `gen_random_uuid()` as a built-in function
+- PostgreSQL 15 is the current stable release and matches our deployment target
+- All schema features (IF NOT EXISTS, CREATE OR REPLACE FUNCTION) work with PostgreSQL 9.5+
+
 ### 1. File Structure: Single Source of Truth
 
 **Decision:** Single `internal/database/schema.go` file referencing existing `database/schema/schema.sql`.
@@ -300,6 +311,7 @@ func executeSchema(ctx context.Context, db *pgxpool.Pool) error {
     
     _, err = tx.Exec(ctx, SchemaFile)
     if err != nil {
+        log.Printf("HINT: Run manually to debug: psql -h localhost -U postgres -d bookhoard -f database/schema/schema.sql")
         return fmt.Errorf("schema execution failed: %w", err)
     }
     
@@ -414,6 +426,53 @@ ls -la ../../database/schema/schema.sql
 # Should show the file exists at the correct relative location
 ```
 
+#### Step 2.3: Add Unit Tests for schema.go
+
+Create `internal/database/schema_test.go`:
+
+```go
+package database
+
+import (
+    "context"
+    "testing"
+    
+    "github.com/jackc/pgx/v5/pgxpool"
+    "github.com/stretchr/testify/assert"
+)
+
+func TestParseTableNames(t *testing.T) {
+    tables, err := parseTableNames()
+    assert.NoError(t, err)
+    assert.Greater(t, len(tables), 20, "Should parse at least 20 tables")
+    
+    // Verify critical tables are detected
+    tableMap := make(map[string]bool)
+    for _, table := range tables {
+        tableMap[table] = true
+    }
+    assert.True(t, tableMap["users"], "Should find 'users' table")
+    assert.True(t, tableMap["libraries"], "Should find 'libraries' table")
+    assert.True(t, tableMap["media_items"], "Should find 'media_items' table")
+}
+
+func TestGenerateLockID(t *testing.T) {
+    result := generateLockID("bookhoard:schema:init")
+    assert.Equal(t, int64(7804706162000639061), result, "FNV-1a hash must match expected value")
+}
+
+func TestVerifyTables_MissingTables(t *testing.T) {
+    // This would require a mock database or test setup
+    // For now, skip or implement with pgxpool mock
+    t.Skip("Requires database connection - implement in integration tests")
+}
+```
+
+Run tests with:
+```bash
+go test ./internal/database -v
+```
+
 ---
 
 ### Phase 3: Integrate into main.go
@@ -481,6 +540,7 @@ func main() {
 - [ ] No schema file duplication (single source of truth)
 - [ ] Verifies critical functions exist, not just tables
 - [ ] Provides clear error messages for missing schema components
+- [ ] Includes debug hint when schema execution fails (psql command)
 
 **Phase 3 Verification:**
 - [ ] `cmd/server/main.go` compiles without errors
@@ -491,7 +551,7 @@ func main() {
 **Integration Testing:**
 - [ ] Fresh database initializes correctly
 - [ ] Existing database doesn't break
-- [ ] Concurrent startup works with advisory locks
+- [ ] Concurrent startup works with advisory locks (manual test below)
 - [ ] Partial state recovers successfully
 - [ ] TestKoboInitialization passes
 - [ ] All integration tests pass
@@ -502,6 +562,32 @@ func main() {
 - [ ] `go build ./...` succeeds for entire project
 - [ ] `bash scripts/verify-guidelines.sh` passes (0 errors)
 
+**Concurrent Startup Test (Manual):**
+```bash
+# Test advisory locks work correctly with multiple instances
+# Start 5 instances simultaneously
+for i in {1..5}; do
+    podman compose -p test$i up -d app
+    sleep 0.5  # Stagger starts slightly
+done
+
+# Wait 10 seconds for all to initialize
+sleep 10
+
+# Check all logs for successful initialization
+for i in {1..5}; do
+    echo "=== Instance $i ==="
+    podman logs test$i_bookhoard_app 2>&1 | grep "schema initialization complete"
+done
+
+# Cleanup
+for i in {1..5}; do
+    podman compose -p test$i down
+done
+```
+
+**Expected result:** All 5 instances should show "schema initialization complete" in logs, proving advisory locks prevent race conditions.
+
 ---
 
 ## 📈 Expected Outcomes
@@ -585,6 +671,23 @@ If new version has schema issues:
 
 ## 📞 Support
 
+### PostgreSQL Version Issues
+
+If you see errors about `gen_random_uuid()` not existing:
+```bash
+# Check PostgreSQL version
+podman exec bookhoard_db psql --version
+# Should be 13.0 or higher
+```
+
+If using an older PostgreSQL version, update `docker-compose.yml`:
+```yaml
+db:
+  image: postgres:15-alpine  # Or postgres:13-alpine minimum
+```
+
+### Troubleshooting
+
 If issues occur:
 
 ### Check logs first:
@@ -623,8 +726,9 @@ podman compose up -d
 ## 📚 Documentation
 
 Create documentation explaining the automatic schema initialization:
-- **docs/contributing/database-schema.md** - How schema initialization works, how to modify schema safely
+- **docs/contributing/database-schema.md** - How schema initialization works, how to modify schema safely, PostgreSQL version requirements
-- **README.md** - Add "Database Initialization" section documenting first-run behavior
+- **README.md** - Add "Database Initialization" section documenting first-run behavior and PostgreSQL version requirements
+- **internal/database/schema_test.go** - Unit tests for schema parsing and verification functions
 
 ---