Add IndexedDB schema migration framework and fix setInterval memory leak in UploadService

[Copilot]

The database was hardcoded at v1 with no upgrade path, making future schema changes unsafe. Separately, clearInterval in uploadAsset was duplicated across try/catch, leaking the interval if anything threw unexpectedly.

IndexedDB migration framework (IndexedDBService.ts)

• Bumped DB_VERSION 1 → 2
• Introduced a migrations map keyed by version; onupgradeneeded now iterates oldVersion+1..newVersion and applies each migration in order
• v1 migration preserves the original store/index creation; v2 adds the uploadAttempts index

const migrations: Record<number, (db: IDBDatabase, tx: IDBTransaction) => void> = {
  1: (db) => {
    const store = db.createObjectStore(STORE_NAME, { keyPath: 'id' });
    store.createIndex('status', 'status', { unique: false });
    // ...
  },
  2: (_db, tx) => {
    const store = tx.objectStore(STORE_NAME);
    if (!store.indexNames.contains('uploadAttempts')) {
      store.createIndex('uploadAttempts', 'uploadAttempts', { unique: false });
    }
  },
};

request.onupgradeneeded = (event) => {
  const db = request.result;
  const tx = request.transaction!;
  for (let v = event.oldVersion + 1; v <= (event.newVersion ?? DB_VERSION); v++) {
    migrations[v]?.(db, tx);
  }
};

Interval cleanup (UploadService.ts)

• Replaced duplicate clearInterval in try + catch with a single call in finally, guaranteeing cleanup on all exit paths including re-thrown errors from handleUploadSuccess

Original prompt

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This section details on the original issue you should resolve

<issue_title>[Feature][Medium] Add IndexedDB schema migration strategy and fix memory leaks in upload progress simulation</issue_title>
<issue_description>## Summary

Two related reliability issues discovered during deep code review:

1. IndexedDB has no schema migration capability — the database is locked at version 1 with no upgrade path, making it impossible to safely add new fields, indexes, or stores in future releases.
2. setInterval memory leak in UploadService — progress simulation intervals can leak if the upload flow throws before the try block or if the error handler itself throws.

Finding 1: No IndexedDB Migration Strategy

Location

src/services/IndexedDBService.ts

Evidence

const DB_VERSION = 1;

request.onupgradeneeded = (event) => {
  const db = (event.target as IDBOpenDBRequest).result;
  if (!db.objectStoreNames.contains(STORE_NAME)) {
    const objectStore = db.createObjectStore(STORE_NAME, { keyPath: 'id' });
    objectStore.createIndex('status', 'status', { unique: false });
    objectStore.createIndex('createdAt', 'createdAt', { unique: false });
  }
};

Problem

• Single version (v1) with no migration functions
• onupgradeneeded only handles initial creation
• Cannot add new required fields or indexes without breaking existing users
• No data transformation on version bump
• The Asset interface uses [key: string]: any as a workaround for extensibility, but this defeats TypeScript safety

Proposed Fix

const DB_VERSION = 2; // Increment when schema changes

const migrations: Record<number, (db: IDBDatabase, tx: IDBTransaction) => void> = {
  1: (db) => {
    const store = db.createObjectStore(STORE_NAME, { keyPath: 'id' });
    store.createIndex('status', 'status', { unique: false });
    store.createIndex('createdAt', 'createdAt', { unique: false });
  },
  2: (db, tx) => {
    const store = tx.objectStore(STORE_NAME);
    store.createIndex('uploadAttempts', 'uploadAttempts', { unique: false });
    // Transform existing records if needed
  },
};

request.onupgradeneeded = (event) => {
  const db = request.result;
  const tx = request.transaction!;
  for (let v = event.oldVersion + 1; v <= event.newVersion!; v++) {
    migrations[v]?.(db, tx);
  }
};

Finding 2: setInterval Memory Leak in Upload Progress

Location

src/services/UploadService.ts:239-296

Evidence

private startProgressSimulation(asset: Asset): ReturnType<typeof setInterval> {
  return setInterval(() => {
    // Updates progress every 500ms
  }, 500);
}

// In uploadAsset():
const progressInterval = this.startProgressSimulation(asset);
try {
  // Upload operations...
  clearInterval(progressInterval);  // Line 245
} catch (error) {
  clearInterval(progressInterval);  // Line 250
  throw error;
}

Problem

• If code before the try block throws (after startProgressSimulation but before entering try), the interval leaks
• If the catch handler itself throws during clearInterval, the interval leaks
• Multiple failed uploads accumulate leaked intervals in the service worker

Proposed Fix

Use try/finally pattern:

const progressInterval = this.startProgressSimulation(asset);
try {
  // Upload operations...
} finally {
  clearInterval(progressInterval);  // Always cleaned up
}

Impact

• Migration: Prevents data corruption when future versions need schema changes; unblocks safe feature development
• Memory leak: Prevents background memory consumption from accumulated intervals in long-running service worker sessions

Files to modify

• src/services/IndexedDBService.ts — add migration framework
• src/services/UploadService.ts — fix interval cleanup pattern</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [Feature][Medium] Add IndexedDB schema migration strategy and fix memory leaks in upload progress simulation #44

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