feat: GitFlow workflow with beta/stable CI pipelines

- Add develop branch for integration
- Replace single ci.yml with 3 workflows: ci-pr (PR checks), ci-develop (beta releases), ci-main (stable releases)
- Add prerelease support in version.go (ldflags injection)
- Add tests for prerelease version formatting
- Document full GitFlow process, versioning, and contributing guide in README

💘 Generated with Crush

Assisted-by: GLM-5.1 via Crush <crush@charm.land>

.gitea/workflows/ci-pr.yml

@@ -0,0 +1,40 @@
+name: PR Check
+
+on:
+  pull_request:
+    branches: [main, develop]
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: '1.24.3'
+
+      - name: Cache Go modules
+        uses: actions/cache@v4
+        with:
+          path: |
+            /root/go/pkg/mod
+            /home/runner/go/pkg/mod
+          key: ${{ runner.os }}-go-${{ hashFiles('**/go.sum') }}
+          restore-keys: |
+            ${{ runner.os }}-go-
+
+      - name: Download dependencies
+        run: go mod download
+
+      - name: Vet
+        run: go vet ./...
+
+      - name: Test
+        run: go test ./... -v -race -timeout 60s
+
+      - name: Build
+        run: |
+          go build -o muyue ./cmd/muyue/
+          ./muyue version