Addresses transient HTTP 500 errors from Gitea API during pattern fetches.

Changes:
- Add retry with exponential backoff (1s, 2s) to doGet(), max 3 attempts
- Add IsServerError() helper to detect 5xx responses
- No retry on 4xx errors (client errors should propagate immediately)
- Respects context cancellation during backoff waits
- Logs retries at WARN level for observability

All existing tests pass. New tests:
- TestIsServerError: validates 5xx detection across edge cases
- TestDoGet_RetriesOn500: verifies recovery after transient errors
- TestDoGet_FailsAfterMaxRetries: verifies proper failure after exhaustion
- TestDoGet_NoRetryOn4xx: ensures client errors don't retry
- TestDoGet_RespectsContextCancellation: validates cancellation during backoff

Closes #68

@@ -210,24 +216,56 @@ func (c *Client) PostReview(ctx context.Context, owner, repo string, number int,
 	return &review, nil
 }
 
+// doGet performs an HTTP GET request with retry on 5xx errors.

@@ -229,0 +239,4 @@
+		req, err := http.NewRequestWithContext(ctx, http.MethodGet, reqURL, nil)
+		if err != nil {
+			return nil, err
+		}

@@ -746,0 +864,4 @@
+	ctx, cancel := context.WithCancel(context.Background())
+	// Cancel immediately after first attempt would trigger retry
+	go func() {
+		time.Sleep(50 * time.Millisecond)

@@ -225,0 +233,4 @@
+			case <-time.After(backoff[attempt]):
+			case <-ctx.Done():
+				return nil, ctx.Err()
+			}

@@ -211,2 +217,4 @@
 }
 
+// doGet performs an HTTP GET request with retry on 5xx errors.
+// Retries up to 3 times with exponential backoff (1s, 2s delays).

@@ -225,0 +227,4 @@
+		if attempt > 0 {
+			slog.Warn("retrying request after server error",
+				"attempt", attempt+1,
+				"url", reqURL,

@@ -229,0 +257,4 @@
+			return body, nil
+		}
+
+		lastErr = &APIError{StatusCode: resp.StatusCode, Body: string(body)}

@@ -210,3 +216,3 @@
 	return &review, nil
 }
-
+// doGet performs an HTTP GET request with retry on 5xx errors.

@@ -229,0 +267,4 @@
+
+		// Error path: limit how much we read from potentially malicious server
+		errBody, _ := io.ReadAll(io.LimitReader(resp.Body, maxErrorBodyBytes))
+		resp.Body.Close()

@@ -746,0 +837,4 @@
+
+	client := NewClient(server.URL, "test-token")
+	_, err := client.doGet(context.Background(), server.URL+"/test")
+	if err == nil {

@@ -209,25 +215,69 @@ func (c *Client) PostReview(ctx context.Context, owner, repo string, number int,
 	}

@@ -219,1 +222,4 @@
+	// backoff[i] is the delay before attempt i+1 (i.e., after attempt i fails).
+	// First attempt (i=0) has no delay; retries wait 1s then 2s.
+	backoff := []time.Duration{1 * time.Second, 2 * time.Second}
 

@@ -46,2 +53,4 @@
 	token   string
 	http    *http.Client
+
+	// RetryBackoff defines the delays between retry attempts.

@@ -229,0 +274,4 @@
+		if attempt > 0 {
+			// Determine delay: use backoff slice if available, otherwise no delay
+			var delay time.Duration
+			if attempt-1 < len(backoff) {

@@ -229,0 +295,4 @@
+			}
+		}
+
+		req, err := http.NewRequestWithContext(ctx, http.MethodGet, reqURL, nil)

@@ -229,0 +307,4 @@
+			// We only retry if there are attempts remaining.
+			if attempt < maxAttempts-1 && isTemporaryNetError(err) {
+				slog.Warn("temporary network error, will retry",
+					"attempt", attempt+1,

@@ -746,0 +904,4 @@
+	ln.Close()
+
+	// Start a server after a short delay to succeed on retry
+	go func() {

@@ -39,12 +40,23 @@ func IsNotFound(err error) bool {
 	return errors.As(err, &apiErr) && apiErr.StatusCode == http.StatusNotFound

@@ -213,0 +231,4 @@
+
+	// Check for common retriable error patterns in the error chain.
+	// Check OpError first since it embeds net.Error, and we want to catch
+	// connection refused, network unreachable, etc. as retriable.

@@ -225,1 +268,4 @@
+	// maxErrorBodyBytes limits how much of an error response body we read
+	// to protect against malicious servers sending unbounded data.
+	const maxErrorBodyBytes = 64 * 1024 // 64 KB
 

@@ -45,3 +53,4 @@
 	baseURL string
 	token   string
 	http    *http.Client
+

@@ -213,0 +280,4 @@
+		}
+	}
+
+	// If we can't identify the specific syscall error, be conservative and retry.

@@ -222,3 +301,1 @@
-		return nil, err
-	}
-	defer resp.Body.Close()
+	// maxErrorBodyBytes limits how much of an error response body we read

@@ -317,9 +462,9 @@ func (c *Client) GetAllFilesInPath(ctx context.Context, owner, repo, path string
 

@@ -746,0 +894,4 @@
+func TestDoGet_RetriesOnTemporaryNetError(t *testing.T) {
+	attempts := 0
+
+	// Create a listener that we can close to simulate connection refused

@@ -210,24 +226,153 @@ func (c *Client) PostReview(ctx context.Context, owner, repo string, number int,
 	return &review, nil

@@ -39,12 +41,26 @@ func IsNotFound(err error) bool {
 	return errors.As(err, &apiErr) && apiErr.StatusCode == http.StatusNotFound

@@ -210,24 +226,153 @@ func (c *Client) PostReview(ctx context.Context, owner, repo string, number int,
 	return &review, nil

@@ -213,0 +293,4 @@
+	parsed, err := url.Parse(rawURL)
+	if err != nil {
+		// If we cannot parse it, return a safe placeholder rather than
+		// potentially logging something sensitive.

@@ -222,3 +317,1 @@
-		return nil, err
-	}
-	defer resp.Body.Close()
+	// maxErrorBodyBytes limits how much of an error response body we read

@@ -229,0 +351,4 @@
+			return nil, err
+		}
+		req.Header.Set("Authorization", "token "+c.token)
+

@@ -746,0 +890,4 @@
+		t.Errorf("attempts = %d, expected 1 before context cancel during backoff", attempts)
+	}
+}
+

@@ -217,1 +312,4 @@
+	backoff := c.RetryBackoff
+	if backoff == nil {
+		backoff = []time.Duration{1 * time.Second, 2 * time.Second}
 	}

@@ -43,4 +51,4 @@
 // A Client is safe for concurrent use by multiple goroutines.
 type Client struct {
 	baseURL string
 	token   string

@@ -213,0 +296,4 @@
+// This prevents accidental exposure of sensitive data that future callers
+// might pass via query strings.
+func redactURL(rawURL string) string {
+	parsed, err := url.Parse(rawURL)

@@ -213,0 +313,4 @@
+// the status code is included; for other errors, the type is preserved.
+func sanitizeErrorForLog(err error) string {
+	if err == nil {
+		return "<nil>"

@@ -746,0 +831,4 @@
+		t.Errorf("status = %d, want 500", apiErr.StatusCode)
+	}
+	if attempts != 3 {
+		t.Errorf("attempts = %d, want 3 (max retries)", attempts)

@@ -746,0 +840,4 @@
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		attempts++
+		w.WriteHeader(http.StatusForbidden)
+		w.Write([]byte(`{"message":"forbidden"}`))

@@ -746,0 +855,4 @@
+	}
+	if apiErr.StatusCode != http.StatusForbidden {
+		t.Errorf("status = %d, want 403", apiErr.StatusCode)
+	}

@@ -56,6 +72,12 @@ func NewClient(baseURL, token string) *Client {
 	}

@@ -213,0 +304,4 @@
+	}
+	if parsed.RawQuery != "" {
+		parsed.RawQuery = "[redacted]"
+	}

@@ -225,1 +337,4 @@
+	// maxErrorBodyBytes limits how much of an error response body we read
+	// to protect against malicious servers sending unbounded data.
+	const maxErrorBodyBytes = 64 * 1024 // 64 KB
 

@@ -746,0 +838,4 @@
+func TestDoGet_NoRetryOn4xx(t *testing.T) {
+	attempts := 0
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		attempts++