Update golangci-lint to v2.12.2 with canonical config (#187)

Bumps golangci-lint from v2.10.1 to v2.12.2 everywhere it is pinned and installs the canonical `.golangci.yml`, then fixes every finding the new linter surfaces so `make check` is green.

## Version pins

- `Dockerfile` lint stage: `golangci/golangci-lint:v2.12.2` (Debian-based), tag plus digest pin
- `script/bootstrap`: `GOLANGCI_LINT_VERSION=2.12.2` with updated `linux-amd64`/`linux-arm64` release-archive sha256 pins

## Config

`.golangci.yml` replaced with the canonical config. Material change: the old file declared `version: "2"` but kept settings under the legacy top-level `linters-settings` key, which golangci-lint v2 ignores — so the intended thresholds (`lll` 88, `funlen` 80/50, `cyclop` 15, `dupl` 100) were not being applied. The canonical file moves them under `linters.settings` and drops `issues.exclude-use-default`.

## Lint fixes (216 findings)

- `lll` (96): wrapped lines to the 88-column limit
- `noctx` (46): `httptest.NewRequestWithContext` with `t.Context()` throughout the tests
- `goconst` (24): shared constants for template/JSON keys in `internal/handlers` and repeated test literals
- `gosec` (23): app-page redirects now go through a `redirectToApp` helper that path-escapes the app ID (G710 open redirect); `http.ServeFile` of the internally derived deployment log path annotated like the adjacent `os.Stat` (G703)
- `dupl` (22): extracted a generic `findAllByAppID` in `internal/models`, a `deleteAppResource` helper in `internal/handlers`, a shared `parsePush` in `internal/service/webhook`, and table-driven/helper-based dedup in tests
- `nolintlint` (5): removed `//nolint:funlen` directives made obsolete by the new limits (plus one more that became obsolete after refactoring)
- `nilerr` (3, surfaced during fixing): resource-delete lookups now propagate the find error to the caller

No behavior changes intended; all tests pass and `make check` is green.

Note: golangci-lint v2.12 warns that `gomodguard` is deprecated in favor of `gomodguard_v2` — a future canonical-config update should address this centrally.
Co-authored-by: sneak <sneak@sneak.berlin>
Reviewed-on: #187
Co-authored-by: clawbot <clawbot@noreply.example.org>
Co-committed-by: clawbot <clawbot@noreply.example.org>

internal/middleware/cors_test.go

@@ -24,21 +24,30 @@ func newCORSTestMiddleware(corsOrigins string) *Middleware {
 	}
 }
 
-func TestCORS_NoOriginsConfigured_NoCORSHeaders(t *testing.T) {
-	t.Parallel()
+// assertNoCORSHeaders runs a request with the given Origin header through
+// CORS middleware configured with corsOrigins and asserts that no
+// Access-Control-Allow-Origin header is set.
+func assertNoCORSHeaders(t *testing.T, corsOrigins, origin, msg string) {
+	t.Helper()
 
-	m := newCORSTestMiddleware("")
+	m := newCORSTestMiddleware(corsOrigins)
 	handler := m.CORS()(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
 		w.WriteHeader(http.StatusOK)
 	}))
 
-	req := httptest.NewRequest(http.MethodGet, "/", nil)
-	req.Header.Set("Origin", "https://evil.com")
+	req := httptest.NewRequestWithContext(t.Context(), http.MethodGet, "/", nil)
+	req.Header.Set("Origin", origin)
 
 	rec := httptest.NewRecorder()
 	handler.ServeHTTP(rec, req)
 
-	assert.Empty(t, rec.Header().Get("Access-Control-Allow-Origin"),
+	assert.Empty(t, rec.Header().Get("Access-Control-Allow-Origin"), msg)
+}
+
+func TestCORS_NoOriginsConfigured_NoCORSHeaders(t *testing.T) {
+	t.Parallel()
+
+	assertNoCORSHeaders(t, "", "https://evil.com",
 		"expected no CORS headers when no origins configured")
 }
 
@@ -50,7 +59,7 @@ func TestCORS_OriginsConfigured_AllowsMatchingOrigin(t *testing.T) {
 		w.WriteHeader(http.StatusOK)
 	}))
 
-	req := httptest.NewRequest(http.MethodGet, "/", nil)
+	req := httptest.NewRequestWithContext(t.Context(), http.MethodGet, "/", nil)
 	req.Header.Set("Origin", "https://app.example.com")
 
 	rec := httptest.NewRecorder()
@@ -65,17 +74,6 @@ func TestCORS_OriginsConfigured_AllowsMatchingOrigin(t *testing.T) {
 func TestCORS_OriginsConfigured_RejectsNonMatchingOrigin(t *testing.T) {
 	t.Parallel()
 
-	m := newCORSTestMiddleware("https://app.example.com")
-	handler := m.CORS()(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
-		w.WriteHeader(http.StatusOK)
-	}))
-
-	req := httptest.NewRequest(http.MethodGet, "/", nil)
-	req.Header.Set("Origin", "https://evil.com")
-
-	rec := httptest.NewRecorder()
-	handler.ServeHTTP(rec, req)
-
-	assert.Empty(t, rec.Header().Get("Access-Control-Allow-Origin"),
+	assertNoCORSHeaders(t, "https://app.example.com", "https://evil.com",
 		"expected no CORS headers for non-matching origin")
 }