Split PR CI into pre-commit, test, and build workflows

Each Woodpecker workflow file maps to one ci/woodpecker/pr/<file> status
context, so break the single build.yaml into three PR workflows to expose
three separate PR checks:

- .woodpecker/pre-commit.yaml runs the pre-commit hooks via make pre-commit.
- .woodpecker/test.yaml runs make test (go test ./...).
- .woodpecker/build.yaml keeps only the container dry-run build-check.

Add .pre-commit-config.yaml (gofmt/go vet/go unit tests + whitespace/yaml
hooks) and a make pre-commit target. docker.yaml (tag release) is unchanged.

.pre-commit-config.yaml

@@ -0,0 +1,17 @@
+repos:
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v4.6.0
+    hooks:
+      - id: trailing-whitespace
+      - id: end-of-file-fixer
+      - id: check-yaml
+      - id: check-merge-conflict
+      - id: mixed-line-ending
+        args: [--fix=lf]
+
+  - repo: https://github.com/dnephin/pre-commit-golang
+    rev: v0.5.1
+    hooks:
+      - id: go-fmt
+      - id: go-vet
+      - id: go-unit-tests