feat: add E2E test suite with nightly CI, fix dashboard Dockerfile

E2E Tests:
- 17 integration tests covering: health, repos CRUD, findings lifecycle,
  cascade delete (SAST + DAST + pentest), DAST targets, stats overview
- TestServer harness: spins up agent API on random port with isolated
  MongoDB database per test, auto-cleanup
- Added lib.rs to expose agent internals for integration tests
- Nightly CI workflow with MongoDB service container (3 AM UTC)

Tests verify:
- Repository add/list/delete + duplicate rejection + invalid ID handling
- Finding creation, filtering by severity/repo, status updates, bulk updates
- Cascade delete: repo deletion removes all DAST targets, pentest sessions,
  attack chain nodes, DAST findings, SAST findings, and SBOM entries
- DAST target CRUD and empty finding list
- Stats overview accuracy with zero and populated data

Also:
- Fix Dockerfile.dashboard: bump dioxus-cli 0.7.3 → 0.7.4 (compile fix)
- Fix clippy: allow new_without_default for pattern scanners

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

.gitea/workflows/nightly.yml

@@ -0,0 +1,52 @@
+name: Nightly E2E Tests
+
+on:
+  schedule:
+    - cron: '0 3 * * *'  # 3 AM UTC daily
+  workflow_dispatch:       # Allow manual trigger
+
+env:
+  CARGO_TERM_COLOR: always
+  RUSTFLAGS: "-D warnings"
+  RUSTC_WRAPPER: /usr/local/bin/sccache
+  SCCACHE_DIR: /tmp/sccache
+  TEST_MONGODB_URI: "mongodb://root:example@mongo:27017/?authSource=admin"
+
+concurrency:
+  group: nightly-e2e
+  cancel-in-progress: true
+
+jobs:
+  e2e:
+    name: E2E Tests
+    runs-on: docker
+    container:
+      image: rust:1.94-bookworm
+    services:
+      mongo:
+        image: mongo:7
+        env:
+          MONGO_INITDB_ROOT_USERNAME: root
+          MONGO_INITDB_ROOT_PASSWORD: example
+    steps:
+      - name: Checkout
+        run: |
+          git init
+          git remote add origin "${GITHUB_SERVER_URL}/${GITHUB_REPOSITORY}.git"
+          git fetch --depth=1 origin "${GITHUB_SHA:-refs/heads/main}"
+          git checkout FETCH_HEAD
+
+      - name: Install sccache
+        run: |
+          curl -fsSL https://github.com/mozilla/sccache/releases/download/v0.9.1/sccache-v0.9.1-x86_64-unknown-linux-musl.tar.gz \
+            | tar xz --strip-components=1 -C /usr/local/bin/ sccache-v0.9.1-x86_64-unknown-linux-musl/sccache
+          chmod +x /usr/local/bin/sccache
+        env:
+          RUSTC_WRAPPER: ""
+
+      - name: Run E2E tests
+        run: cargo test -p compliance-agent --test e2e -- --test-threads=4
+
+      - name: Show sccache stats
+        run: sccache --show-stats
+        if: always()