Add interactive modal for viewing Instagram posts with full details

Refactor database configuration to support PostgreSQL and fallback to MySQL, and enhance Instagram model to include full captions and link posts to a new Bootstrap modal for interactive viewing.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: 71ce66a1-5143-4571-9fb1-9e0ee4859532
Replit-Commit-Checkpoint-Type: full_checkpoint
Replit-Commit-Event-Id: ea3639ff-1e5a-4e02-990a-688fde87bfaf
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/405e5ffd-f893-49b7-ab72-765c75901842/71ce66a1-5143-4571-9fb1-9e0ee4859532/A5OtlGZ
