Add configuration template files (.env.example, .dockerignore)

Added essential configuration templates that were missing from the
repository due to overly restrictive .gitignore patterns.

Changes to .gitignore:
- Added negation patterns for .env.example files
- Added negation patterns for .dockerignore files
- These are safe template files with placeholder values

Files added:
- .env.example (root): Main environment configuration template
- reports-app/backend/.env.example: Backend configuration template
- reports-app/frontend/.env.example: Frontend configuration template
- reports-app/telegram-bot/.env.example: Telegram bot config template
- reports-app/telegram-bot/.dockerignore: Docker build exclusions

These template files help developers quickly set up their local
development environment by copying and customizing them.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

.gitignore

@@ -247,7 +247,6 @@ quick_test.*
 .dmypy.json
 .docker/
 .dockerignore
-.dockerignore
 .eggs/
 .eggs/
 .env
@@ -258,6 +257,12 @@ quick_test.*
 .env.production
 .env.production
 .env.test
+# Allow .env.example files (configuration templates)
+!.env.example
+!**/.env.example
+# Allow .dockerignore files (Docker build configuration)
+!.dockerignore
+!**/.dockerignore
 .gcp/
 .hypothesis/
 .hypothesis/