feat: add build/test CI pipeline and dependabot

- Add .NET CI pipeline (restore, build --warnaserror, test on JP branch)
- Add Dependabot for nuget and github-actions ecosystems

Co-Authored-By: Svrnty Inc. <eng@svrnty.com>

.github/dependabot.yml

@@ -0,0 +1,35 @@
+version: 2
+
+updates:
+  - package-ecosystem: nuget
+    directory: "/"
+    schedule:
+      interval: weekly
+    target-branch: JP
+    open-pull-requests-limit: 3
+    labels:
+      - "dependencies"
+    groups:
+      nuget-all:
+        patterns:
+          - "*"
+        update-types:
+          - minor
+          - patch
+
+  - package-ecosystem: github-actions
+    directory: "/"
+    schedule:
+      interval: weekly
+    target-branch: JP
+    open-pull-requests-limit: 1
+    labels:
+      - "ci"
+      - "dependencies"
+    groups:
+      actions-all:
+        patterns:
+          - "*"
+        update-types:
+          - minor
+          - patch

.github/workflows/ci.yml

@@ -15,13 +15,13 @@ jobs:
 
       - uses: actions/setup-dotnet@v4
         with:
-          dotnet-version: '10.0.x'
+          dotnet-version: "8.x"
 
-      - name: Restore dependencies
-        run: dotnet restore
+      - name: Restore
+        run: dotnet restore Svrnty.CQRS.sln
 
-      - name: Build (warnings as errors)
-        run: dotnet build --no-restore --warnaserror
+      - name: Build
+        run: dotnet build Svrnty.CQRS.sln --no-restore --warnaserror
 
       - name: Test
-        run: dotnet test --no-build --verbosity normal
+        run: dotnet test Svrnty.CQRS.sln --no-build --verbosity normal