fix: comprehensive bug fixes and architecture restructuring

Phase 1 — Bug fixes (7 bugs):
- Bug 1: Pulsar mode data loss — always persist to SQLite regardless of mode
- Bug 2: PulsarSend closing TCP client — use independent resetPulsarProducer()
- Bug 3: Greedy regex — use non-greedy (?s)ZCZC.*?NNNN
- Bug 4: Data after NNNN discarded — keep remaining buffer data
- Bug 5: strings.Index > 0 boundary — use strings.Contains
- Bug 6: Variable shadowing in PulsarSend — use = not :=
- Bug 7: Accept failure nil panic — add continue + retry logic

Phase 2 — Architecture restructuring:
- Split utils/ into config/, serial/, telegram/, storage/, transport/
- Define Sender, Repository, Reader interfaces
- Introduce app/ layer with context.Context lifecycle
- Replace spinlock with sync.Mutex
- Unified Config struct replaces 15+ global vars

Phase 3 — Testing & tooling:
- telegram/parser_test.go (7 test cases)
- storage/store_test.go (5 test cases)
- transport/transport_test.go (4 test cases)
- Taskfile: add test, test-race, test-cover tasks
- Go version: 1.15 -> 1.21

config/config.go

@@ -0,0 +1,43 @@
+package config
+
+// Config holds all application configuration.
+type Config struct {
+	Serial  SerialConfig
+	Telegram TelegramConfig
+	SQLite  SQLiteConfig
+	Socket  SocketConfig
+	Pulsar  PulsarConfig
+	Log     LogConfig
+}
+
+type SerialConfig struct {
+	Device   string
+	Baudrate int
+	LogRaw   bool
+}
+
+type TelegramConfig struct {
+	TCP    bool
+	Pulsar bool
+}
+
+type SQLiteConfig struct {
+	File string
+	Init bool
+}
+
+type SocketConfig struct {
+	Address string
+}
+
+type PulsarConfig struct {
+	URL   string
+	Topic string
+	Name  string
+}
+
+type LogConfig struct {
+	Dir       string
+	MaxAge    int // days
+	RotateHour int
+}