Implement Phase 1 of KAT (#1)

**Phase 1: State Management & Leader Election**
*   **Goal**: A functional embedded etcd and leader election mechanism.
*   **Tasks**:
    1.  Implement the `StateStore` interface (RFC 5.1) with an etcd backend (`internal/store/etcd.go`).
    2.  Integrate embedded etcd server into `kat-agent` (RFC 2.2, 5.2), configurable via `cluster.kat` parameters.
    3.  Implement leader election using `go.etcd.io/etcd/client/v3/concurrency` (RFC 5.3).
    4.  Basic `kat-agent init` functionality:
        *   Parse `cluster.kat`.
        *   Start single-node embedded etcd.
        *   Campaign for and become leader.
        *   Store initial cluster configuration (UID, CIDRs from `cluster.kat`) in etcd.
*   **Milestone**:
    *   A single `kat-agent init --config cluster.kat` process starts, initializes etcd, and logs that it has become the leader.
    *   The cluster configuration from `cluster.kat` can be verified in etcd using an etcd client.
    *   `StateStore` interface methods (`Put`, `Get`, `Delete`, `List`) are testable against the embedded etcd.

Reviewed-on: #1

.gitea/workflows/test_integration.yml

@@ -0,0 +1,28 @@
+name: Integration Tests
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  integration-tests:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+
+    - name: Set up Go
+      uses: actions/setup-go@v4
+      with:
+        go-version: '1.24'
+
+    - name: Install dependencies
+      run: go mod download
+
+    - name: Run integration tests
+      run: go test -count=1 -run Integration ./... -v -coverprofile=coverage.out
+    
+    - name: Print coverage report
+      run: go tool cover -func=coverage.out
+      continue-on-error: true

.gitea/workflows/test_unit.yml

@@ -0,0 +1,28 @@
+name: Unit Tests
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  unit-tests:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+
+    - name: Set up Go
+      uses: actions/setup-go@v4
+      with:
+        go-version: '1.24'
+
+    - name: Install dependencies
+      run: go mod download
+
+    - name: Run unit tests
+      run: go test -v ./... -coverprofile=coverage.out
+
+    - name: Print coverage report
+      run: go tool cover -func=coverage.out
+      continue-on-error: true