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/bom-decomposition/README.md

@@ -27,25 +27,6 @@ Project-specific aliases are acceptable if the semantics stay identical:
 - `component_mappings` -> `lot_mappings`
 - `quantity_per_item` -> `quantity_per_pn`
 
-## Persistence Example
-
-```json
-{
-  "vendor_spec": [
-    {
-      "sort_order": 10,
-      "vendor_partnumber": "ABC-123",
-      "quantity": 2,
-      "description": "Bundle",
-      "lot_mappings": [
-        { "lot_name": "LOT_CPU", "quantity_per_pn": 1 },
-        { "lot_name": "LOT_RAIL", "quantity_per_pn": 1 }
-      ]
-    }
-  ]
-}
-```
-
 ## Wrong Shape
 
 ```json