docs: Remove outdated architecture and documentation files

- Delete several obsolete documents, including `design-patterns.md`, `HF_FREE_TIER_ANALYSIS.md`, `overview.md`, `deployment.md`, and `workflow-diagrams.md`, as they no longer align with the current project structure and objectives.
- This cleanup enhances the clarity and relevance of the documentation for developers and stakeholders.

docs/specs/SPEC-20-PUBMED-JSON-FIX.md

@@ -1,6 +1,6 @@
 # SPEC-20: PubMed JSON Parsing Fix
 
-**Status:** READY FOR IMPLEMENTATION
+**Status:** COMPLETED
 **Priority:** P2 (Critical - causes crashes)
 **Effort:** 15 minutes
 **PR Scope:** Single file fix