refactor(server): decouple services and improve architecture

- Introduce interfaces for all major services (JWT, PostAI, Comment, Message, Notification, QRCodeLogin, Upload, Vote, etc.) to support dependency inversion.
- Move query parameters from `internal/dto` to a new `internal/query` package to separate request payloads from data transfer objects.
- Refactor `internal/router` to use embedded `RouterDeps` for cleaner dependency management.
- Decouple handlers from repositories by injecting services instead of direct repository access, ensuring proper layering.
- Improve database initialization by moving it from `internal/model` to `internal/database`.
- Optimize message decryption by implementing a more efficient `BatchDecrypt` method in `MessageEncryptor` using a worker pool.
- Enhance error handling and security by implementing fail-fast checks for encryption key length during startup.
- Clean up unused code, including the `avatar` package and several unused DTOs.

internal/model/message_crypto_test.go

@@ -0,0 +1,140 @@
+package model
+
+import (
+	"encoding/json"
+	"testing"
+
+	"with_you/internal/pkg/crypto"
+)
+
+const testKey = "12345678901234567890123456789012"
+
+// initEnc 初始化（幂等，因 crypto 用 sync.Once）加密器。
+func initEnc(t *testing.T) {
+	t.Helper()
+	if err := crypto.InitMessageEncryptor(testKey, 1); err != nil {
+		t.Fatalf("InitMessageEncryptor: %v", err)
+	}
+	if crypto.GetMessageEncryptor() == nil {
+		t.Fatal("encryptor not initialized")
+	}
+}
+
+// TestMessage_EncryptDecryptRoundTrip 验证：BeforeCreate 加密落库 →
+// 清空内存 Segments → Decrypt 还原 → 内容与原文一致。
+func TestMessage_EncryptDecryptRoundTrip(t *testing.T) {
+	initEnc(t)
+
+	original := MessageSegments{
+		{Type: "text", Data: MessageSegmentData{"content": "你好世界"}},
+		{Type: "image", Data: MessageSegmentData{"url": "https://example.com/a.png"}},
+	}
+
+	msg := &Message{Segments: original}
+
+	// 模拟 GORM 创建钩子：加密
+	if err := msg.BeforeCreate(nil); err != nil {
+		t.Fatalf("BeforeCreate (encrypt) failed: %v", err)
+	}
+
+	// 加密后应写入 SegmentsEncrypted，且不应是明文 JSON（除非降级）
+	if msg.SegmentsEncrypted == "" {
+		t.Fatal("SegmentsEncrypted should be populated after BeforeCreate")
+	}
+	// 校验确实加密了：明文 JSON 中应包含 "content"，密文 base64 中不应直接出现该明文
+	if contains(msg.SegmentsEncrypted, "你好世界") {
+		t.Errorf("SegmentsEncrypted appears to contain plaintext: %q", msg.SegmentsEncrypted)
+	}
+	if msg.SegmentsKeyVersion != crypto.GetMessageEncryptor().GetKeyVersion() {
+		t.Errorf("SegmentsKeyVersion = %d, want %d",
+			msg.SegmentsKeyVersion, crypto.GetMessageEncryptor().GetKeyVersion())
+	}
+
+	// 模拟从 DB 取回后清空内存段（仅 SegmentsEncrypted 落库）
+	msg.Segments = nil
+	msg.decrypted = false
+
+	// 解密还原
+	if err := msg.Decrypt(); err != nil {
+		t.Fatalf("Decrypt failed: %v", err)
+	}
+
+	if len(msg.Segments) != len(original) {
+		t.Fatalf("after Decrypt, len(Segments) = %d, want %d", len(msg.Segments), len(original))
+	}
+	for i, seg := range msg.Segments {
+		if seg.Type != original[i].Type {
+			t.Errorf("segment[%d].Type = %q, want %q", i, seg.Type, original[i].Type)
+		}
+		if seg.Data["content"] != original[i].Data["content"] {
+			t.Errorf("segment[%d].content mismatch: got %v, want %v",
+				i, seg.Data["content"], original[i].Data["content"])
+		}
+	}
+}
+
+// TestMessage_EncryptEmptySegments 验证：空 Segments 时加密为 no-op。
+func TestMessage_EncryptEmptySegments(t *testing.T) {
+	initEnc(t)
+
+	msg := &Message{}
+	if err := msg.BeforeCreate(nil); err != nil {
+		t.Fatalf("BeforeCreate failed: %v", err)
+	}
+	if msg.SegmentsEncrypted != "" {
+		t.Errorf("empty Segments should not produce ciphertext, got %q", msg.SegmentsEncrypted)
+	}
+}
+
+// TestBatchDecryptMessagesParallel_RoundTrip 验证批量解密路径与单条一致。
+func TestBatchDecryptMessagesParallel_RoundTrip(t *testing.T) {
+	initEnc(t)
+
+	contents := []string{"消息A", "消息B", "消息C"}
+	msgs := make([]*Message, len(contents))
+	for i, c := range contents {
+		m := &Message{
+			Segments: MessageSegments{
+				{Type: "text", Data: MessageSegmentData{"content": c}},
+			},
+		}
+		if err := m.BeforeCreate(nil); err != nil {
+			t.Fatalf("BeforeCreate[%d]: %v", i, err)
+		}
+		m.Segments = nil // 模拟从 DB 取回
+		msgs[i] = m
+	}
+
+	BatchDecryptMessagesParallel(msgs)
+
+	for i, m := range msgs {
+		if !m.decrypted {
+			t.Errorf("msg[%d] not marked decrypted", i)
+		}
+		if len(m.Segments) != 1 {
+			t.Errorf("msg[%d] segments len = %d, want 1", i, len(m.Segments))
+			continue
+		}
+		if got := m.Segments[0].Data["content"]; got != contents[i] {
+			t.Errorf("msg[%d].content = %v, want %q", i, got, contents[i])
+		}
+	}
+}
+
+// contains 简单子串判断（避免引入 strings 仅为此）。
+func contains(s, sub string) bool {
+	return len(s) >= len(sub) && (indexOf(s, sub) >= 0)
+}
+
+func indexOf(s, sub string) int {
+	bs := []byte(s)
+	for i := 0; i+len(sub) <= len(bs); i++ {
+		if string(bs[i:i+len(sub)]) == sub {
+			return i
+		}
+	}
+	return -1
+}
+
+// 编译期保证 json 被使用（兼容路径用到）。
+var _ = json.Marshal