feat: Concurrent file analysis with rate limiting, retries, and rich progress bar

[CodeMaverick-143]

Feature Request

Implement asynchronous or multi-threaded concurrent analysis with automatic exponential backoff retries and a rich progress bar.

Problem with Current Implementation

Currently, insight/analyzer.py loops over all files sequentially:

for idx, file_path in enumerate(files, start=1):
    results.append(analyze_file(file_path))

In repos with 50–100 files, sequential network requests to the Gemini API take multiple minutes. Furthermore, bursts of requests can trigger HTTP 429 (Rate Limit) errors with no retry or backoff handling.

Proposed Solution

1. Use concurrent.futures.ThreadPoolExecutor(max_workers=5) (or asyncio).
2. Add exponential backoff retry for HTTP 429 and network errors.
3. Integrate rich.progress.Progress for an interactive, animated terminal progress bar showing ETA, percentage, and current processing file.