fix: remove all SQLite references (migrate.ts, migration script, package.json)

.agents/skills/code-reviewer/references/common-issues.md

@@ -0,0 +1,142 @@
+# Common Issues
+
+## N+1 Query Problem
+
+```typescript
+// N+1 queries - BAD
+const posts = await Post.findAll();
+for (const post of posts) {
+  post.author = await User.findById(post.authorId); // N queries!
+}
+
+// Single query with join - GOOD
+const posts = await Post.findAll({ include: [User] });
+
+// Or batch load
+const posts = await Post.findAll();
+const authorIds = posts.map(p => p.authorId);
+const authors = await User.findByIds(authorIds);
+```
+
+## Missing Error Handling
+
+```typescript
+// Unhandled rejection - BAD
+const data = await fetch('/api/data').then(r => r.json());
+
+// Proper error handling - GOOD
+try {
+  const response = await fetch('/api/data');
+  if (!response.ok) {
+    throw new Error(`HTTP ${response.status}`);
+  }
+  const data = await response.json();
+} catch (error) {
+  logger.error('Failed to fetch data', { error });
+  throw new DataFetchError('Could not load data');
+}
+```
+
+## Magic Numbers/Strings
+
+```typescript
+// Magic number - BAD
+if (user.age >= 18) { ... }
+setTimeout(fn, 86400000);
+
+// Named constant - GOOD
+const MINIMUM_AGE = 18;
+const ONE_DAY_MS = 24 * 60 * 60 * 1000;
+
+if (user.age >= MINIMUM_AGE) { ... }
+setTimeout(fn, ONE_DAY_MS);
+```
+
+## Deep Nesting
+
+```typescript
+// Deep nesting - BAD
+if (user) {
+  if (user.isActive) {
+    if (user.hasPermission) {
+      doSomething();
+    }
+  }
+}
+
+// Early returns - GOOD
+if (!user || !user.isActive || !user.hasPermission) {
+  return;
+}
+doSomething();
+```
+
+## God Functions
+
+```typescript
+// Does too much - BAD
+async function processOrder(order) {
+  // validate
+  // check inventory
+  // process payment
+  // send email
+  // update database
+  // log analytics
+}
+
+// Single responsibility - GOOD
+async function processOrder(order) {
+  await validateOrder(order);
+  await reserveInventory(order);
+  await chargePayment(order);
+  await sendConfirmation(order);
+}
+```
+
+## Mutable Shared State
+
+```typescript
+// Shared mutable - BAD
+const config = { debug: false };
+function enableDebug() {
+  config.debug = true;
+}
+
+// Immutable pattern - GOOD
+function createConfig(overrides = {}) {
+  return Object.freeze({ debug: false, ...overrides });
+}
+```
+
+## Missing Null Checks
+
+```typescript
+// Unsafe access - BAD
+const name = user.profile.name;
+
+// Safe access - GOOD
+const name = user?.profile?.name ?? 'Unknown';
+```
+
+## Synchronous File Operations
+
+```typescript
+// Blocks event loop - BAD
+const data = fs.readFileSync('file.txt');
+
+// Non-blocking - GOOD
+const data = await fs.promises.readFile('file.txt');
+```
+
+## Quick Reference
+
+| Issue | Impact | Fix |
+|-------|--------|-----|
+| N+1 queries | Performance | Eager load or batch |
+| Missing error handling | Reliability | Try/catch + logging |
+| Magic numbers | Maintainability | Named constants |
+| Deep nesting | Readability | Early returns |
+| God functions | Testability | Single responsibility |
+| Mutable shared state | Bugs | Immutable patterns |
+| Missing null checks | Crashes | Optional chaining |
+| Sync file operations | Performance | Async operations |