Phase 1: config loading, database migrations, audit log

- internal/config: TOML config with env overrides (MCR_ prefix),
  required field validation, same-filesystem check, defaults
- internal/db: SQLite via modernc.org/sqlite, WAL mode, 2 migrations
  (core registry tables + policy/audit), foreign key cascades
- internal/db: audit log write/list with filtering and pagination
- deploy/examples/mcr.toml: annotated example configuration
- .golangci.yaml: disable fieldalignment (readability over micro-opt)
- checkpoint skill copied from mcias

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.claude/skills/checkpoint/SKILL.md

@@ -0,0 +1,8 @@
+# Checkpoint Skill
+
+1. Run `go build ./...`  abort if errors
+2. Run `go test ./...`  abort if failures
+3. Run `go vet ./...`
+4. Run `git add -A && git status`  show user what will be committed
+5. Generate an appropriate commit message based on your instructions.
+6. Run `git commit -m "<message>"` and verify with `git log -1`