Add log ingestion tool for loading signature logs into SQLite

- Parse signature messages from log files extracting app info, device
  details, and feature flags (autofill, touchID, offline login, etc.)
- Support both plain .log and gzip compressed .log.gz files
- File discovery by date range (YYYY/mm/dd directory structure)
- Batch inserts for performance with large files (10GB+ per day)
- Index on session_id and version for efficient queries
- Extensible parser architecture via MessageParser trait
- Parallel file processing for multi-day ingestion

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.github/dependabot.yaml

@@ -0,0 +1,14 @@
+version: 2
+updates:
+  - package-ecosystem: github-actions
+    directory: /
+    schedule:
+      interval: weekly
+      time: "07:00"
+      timezone: "Asia/Tokyo"
+  - package-ecosystem: cargo
+    directory: /
+    schedule:
+      interval: weekly
+      time: "07:00"
+      timezone: "Asia/Tokyo"