Add CI workflow

.github/dependabot.yml

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+version: 2
+updates:
+  - package-ecosystem: github-actions
+    directory: /
+    schedule:
+      interval: weekly

.github/workflows/ci.yml

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+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  build:
+    name: Test & Build
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+
+      - uses: actions/setup-java@be666c2fcd27ec809703dec50e508c2fdc7f6654 # v5.2.0
+        with:
+          distribution: temurin
+          java-version: 21
+
+      - uses: gradle/actions/setup-gradle@0723195856401067f7a2779048b490ace7a47d7c # v5.0.2
+        with:
+          validate-wrappers: true
+
+      - name: Run tests
+        run: ./gradlew test
+
+      - name: Build proxy JAR
+        run: ./gradlew shadowJar
+
+      - name: Upload test reports
+        if: failure()
+        uses: actions/upload-artifact@bbbca2ddaa5d8feaa63e36b76fdaad77386f024f # v7.0.0
+        with:
+          name: test-reports
+          path: build/reports/tests/
+          retention-days: 7
+
+      - name: Upload proxy JAR
+        uses: actions/upload-artifact@bbbca2ddaa5d8feaa63e36b76fdaad77386f024f # v7.0.0
+        with:
+          name: mcp-proxy
+          path: build/libs/mcp-proxy-*.jar
+          retention-days: 30
+
+  dependency-submission:
+    name: Dependency Submission
+    runs-on: ubuntu-latest
+    if: github.ref == 'refs/heads/main' && github.event_name == 'push'
+    permissions:
+      contents: write
+
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+
+      - uses: actions/setup-java@be666c2fcd27ec809703dec50e508c2fdc7f6654 # v5.2.0
+        with:
+          distribution: temurin
+          java-version: 21
+
+      - uses: gradle/actions/dependency-submission@0723195856401067f7a2779048b490ace7a47d7c # v5.0.2