refactor: rewrite project from Rust to Go

- Replace Axum with Chi router
- Replace sqlx with pgx for PostgreSQL
- Replace tonic/prost with grpc-go
- Replace tracing with zerolog
- Update flake.nix for Go build with protoc generation
- Preserve all existing endpoints and functionality

Stack: Chi, pgx, grpc-go, zerolog, yaml.v3

internal/torrent/stub.go

@@ -0,0 +1,90 @@
+package torrent
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"sync"
+	"time"
+)
+
+type StubClient struct {
+	logPath  string
+	savePath string
+	mu       sync.Mutex
+}
+
+func NewStubClient(logPath, savePath string) *StubClient {
+	return &StubClient{
+		logPath:  logPath,
+		savePath: savePath,
+	}
+}
+
+func (c *StubClient) log(format string, args ...any) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	f, err := os.OpenFile(c.logPath, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
+	if err != nil {
+		return
+	}
+	defer f.Close()
+
+	timestamp := time.Now().Format(time.RFC3339)
+	msg := fmt.Sprintf(format, args...)
+	fmt.Fprintf(f, "[%s] %s\n", timestamp, msg)
+}
+
+func (c *StubClient) Connect(ctx context.Context) error {
+	c.log("CONNECT")
+	return nil
+}
+
+func (c *StubClient) Disconnect(ctx context.Context) error {
+	c.log("DISCONNECT")
+	return nil
+}
+
+func (c *StubClient) ListTorrents(ctx context.Context) ([]TorrentInfo, error) {
+	c.log("LIST_TORRENTS")
+	return []TorrentInfo{}, nil
+}
+
+func (c *StubClient) GetTorrent(ctx context.Context, hash string) (*TorrentInfo, error) {
+	c.log("GET_TORRENT hash=%s", hash)
+	return nil, ErrTorrentNotFound
+}
+
+func (c *StubClient) AddTorrentURL(ctx context.Context, url string, savePath *string) error {
+	path := c.savePath
+	if savePath != nil {
+		path = *savePath
+	}
+	c.log("ADD_TORRENT_URL url=%s save_path=%s", url, path)
+	return nil
+}
+
+func (c *StubClient) AddTorrentFile(ctx context.Context, data []byte, savePath *string) error {
+	path := c.savePath
+	if savePath != nil {
+		path = *savePath
+	}
+	c.log("ADD_TORRENT_FILE size=%d save_path=%s", len(data), path)
+	return nil
+}
+
+func (c *StubClient) RemoveTorrent(ctx context.Context, hash string, deleteFiles bool) error {
+	c.log("REMOVE_TORRENT hash=%s delete_files=%t", hash, deleteFiles)
+	return nil
+}
+
+func (c *StubClient) PauseTorrent(ctx context.Context, hash string) error {
+	c.log("PAUSE_TORRENT hash=%s", hash)
+	return nil
+}
+
+func (c *StubClient) ResumeTorrent(ctx context.Context, hash string) error {
+	c.log("RESUME_TORRENT hash=%s", hash)
+	return nil
+}