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-database/contract.md

@@ -1,6 +1,6 @@
 # Contract: Database Patterns (Go / MySQL / MariaDB)
 
-Version: 1.9
+Version: 1.10
 
 See `README.md` for examples, migration snippets, and Docker test commands.
 
@@ -20,7 +20,6 @@ See `README.md` for examples, migration snippets, and Docker test commands.
 - Backup storage, retention, archive format, and restore-readiness must follow `backup-management`.
 - Before applying any unapplied migrations, take and verify a full DB backup.
 - Before applying a migration step that changes a table, take a targeted backup of each affected table.
-- Before writing any backup, verify that the output path resolves outside the git worktree and is not tracked or staged in git.
 - If any migration step in a session fails, roll back all steps applied in that session in reverse order.
 - If rollback is not sufficient, restore from the targeted backup taken before the failing step.
 - After rollback or restore, the DB must be back in the same state it had before the session started.