chore(ci): migrate from Dependabot to Renovate

Replace Dependabot with Renovate for improved dependency management:
- Smart grouping of related packages (Tauri, React, TailwindCSS, etc.)
- Automerge for low-risk updates (patch/minor for dev deps, patch for prod)
- Weekly scheduling with lock file maintenance
- Enhanced security update handling
- Support for pnpm and Cargo ecosystems

.github/dependabot.yml

@@ -1,43 +0,0 @@
-version: 2
-updates:
-  # Enable version updates for npm
-  - package-ecosystem: "npm"
-    directory: "/"
-    schedule:
-      interval: "weekly"
-    open-pull-requests-limit: 10
-    reviewers:
-      - "dependabot[bot]"
-    assignees:
-      - "dependabot[bot]"
-    commit-message:
-      prefix: "chore"
-      include: "scope"
-
-  # Enable version updates for Cargo
-  - package-ecosystem: "cargo"
-    directory: "/src-tauri"
-    schedule:
-      interval: "weekly"
-    open-pull-requests-limit: 10
-    reviewers:
-      - "dependabot[bot]"
-    assignees:
-      - "dependabot[bot]"
-    commit-message:
-      prefix: "chore"
-      include: "scope"
-
-  # Enable version updates for GitHub Actions
-  - package-ecosystem: "github-actions"
-    directory: "/"
-    schedule:
-      interval: "weekly"
-    open-pull-requests-limit: 5
-    reviewers:
-      - "dependabot[bot]"
-    assignees:
-      - "dependabot[bot]"
-    commit-message:
-      prefix: "chore"
-      include: "scope"