chore: remove Dependabot configuration

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

.github/dependabot.yml

@@ -1,24 +0,0 @@
-version: 2
-updates:
-  - package-ecosystem: cargo
-    directory: /
-    schedule: { interval: weekly }
-    groups:
-      rustcrypto:
-        patterns:
-          - sha2
-          - sha1
-          - md-5
-          - hmac
-          - pbkdf2
-          - ripemd
-          - aes
-          - argon2
-          - cipher
-          - digest
-  - package-ecosystem: cargo
-    directory: /apps/gui/src-tauri
-    schedule: { interval: weekly }
-  - package-ecosystem: github-actions
-    directory: /
-    schedule: { interval: weekly }