Deduplicate overlapping rules across contracts

Each rule now has one owning contract; others point to it:
validation and multi-step rules live in forms-validation (modal-workflows
references them), pagination metadata lives in go-api (table-management
references it), the async task flow lives in go-background-tasks (go-api
references it), backup git-safety checks live in backup-management
(go-database references it). Remove the leftover Vapor/Aqua baseline
mention and stale kit/patterns paths, compress the batch-file-upload ADR
narrative, and drop content-free pattern READMEs.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

rules/patterns/go-code-style/contract.md

@@ -1,6 +1,6 @@
 # Contract: Go Code Style and Project Conventions
 
-Version: 1.1
+Version: 1.2
 
 ## Source Text and Comments
 
@@ -11,7 +11,7 @@ Version: 1.1
 
 ## Logging
 
-See `kit/patterns/go-logging/contract.md` for full rules.
+See the `go-logging` contract for full rules.
 
 Summary: use `slog`, log to stdout/stderr (binary console), never to browser console.