Harden distributed file-processing architecture

[adhakshinamoorthy]

What changed

• Externalized PostgreSQL, RabbitMQ, MinIO, JWT, and API-key credentials.
• Added CI, Dependabot, governance documents, architecture guidance, ADRs, and verification scope.
• Replaced full in-memory upload buffering with temporary-file spooling.
• Removed 549 committed build artifacts and added durable ignore rules.
• Formatted the C# source and documented the database-to-broker atomicity gap.

Validation

• Release build: 0 warnings, 0 errors
• Tests: 4 passed
• Formatting and Compose validation passed
• NuGet audit: no known vulnerable packages
• Local Markdown links resolved

Remaining boundary

A live PostgreSQL/RabbitMQ/MinIO/ClamAV/Tesseract test was not executed. Database commit and queue publish remain non-atomic until the proposed outbox dispatcher is implemented.