feat: 添加 AI 分类功能，支持交易自动分类与标签生成

src/services/ai/aiProvider.js

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+export class AiProvider {
+  async enrichTransaction() {
+    throw new Error('AI provider is not implemented')
+  }
+}

src/services/ai/aiService.js

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+import { buildTransactionEnrichmentMessages } from '../../lib/aiPrompt.js'
+import { useSettingsStore } from '../../stores/settings.js'
+import {
+  applyAiEnrichment,
+  fetchRecentTransactionsForAi,
+  markTransactionAiFailed,
+} from '../transactionService.js'
+import { DeepSeekProvider } from './deepseekProvider.js'
+
+const clampThreshold = (value) => {
+  const numeric = Number(value)
+  if (!Number.isFinite(numeric)) return 0.9
+  return Math.min(Math.max(numeric, 0), 1)
+}
+
+const createProvider = (settingsStore) => {
+  if (settingsStore.aiProvider !== 'deepseek') {
+    throw new Error(`Unsupported AI provider: ${settingsStore.aiProvider}`)
+  }
+
+  return new DeepSeekProvider({
+    apiKey: settingsStore.aiApiKey,
+    model: settingsStore.aiModel,
+  })
+}
+
+export const isAiReady = (settingsStore = useSettingsStore()) =>
+  !!settingsStore.aiAutoCategoryEnabled && !!settingsStore.aiApiKey
+
+export const maybeEnrichTransactionWithAi = async (transaction) => {
+  if (!transaction?.id) return transaction
+
+  const settingsStore = useSettingsStore()
+  if (!isAiReady(settingsStore)) {
+    return transaction
+  }
+
+  try {
+    const provider = createProvider(settingsStore)
+    const similarTransactions = await fetchRecentTransactionsForAi(6, transaction.id)
+    const messages = buildTransactionEnrichmentMessages({
+      transaction,
+      similarTransactions,
+    })
+    const result = await provider.enrichTransaction({ messages })
+    const threshold = clampThreshold(settingsStore.aiAutoApplyThreshold)
+
+    const updated = await applyAiEnrichment(transaction.id, result.normalized, {
+      applyCategory: result.normalized.confidence >= threshold,
+      model: result.model,
+    })
+
+    return updated || transaction
+  } catch (error) {
+    console.warn('[ai] transaction enrichment failed', error)
+    const failed = await markTransactionAiFailed(
+      transaction.id,
+      error?.message || 'AI enrichment failed',
+      settingsStore.aiModel,
+    )
+    return failed || transaction
+  }
+}

src/services/ai/deepseekProvider.js

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+import { normalizeEnrichmentResult } from '../../lib/aiPrompt.js'
+import { AiProvider } from './aiProvider.js'
+
+export class DeepSeekProvider extends AiProvider {
+  constructor({ apiKey, baseUrl = 'https://api.deepseek.com', model = 'deepseek-chat' }) {
+    super()
+    this.apiKey = apiKey
+    this.baseUrl = baseUrl.replace(/\/$/, '')
+    this.model = model
+  }
+
+  async enrichTransaction({ messages }) {
+    if (!this.apiKey) {
+      throw new Error('DeepSeek API key is required')
+    }
+
+    const response = await fetch(`${this.baseUrl}/chat/completions`, {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json',
+        Authorization: `Bearer ${this.apiKey}`,
+      },
+      body: JSON.stringify({
+        model: this.model,
+        temperature: 0.2,
+        response_format: { type: 'json_object' },
+        messages,
+      }),
+    })
+
+    if (!response.ok) {
+      const detail = await response.text().catch(() => '')
+      throw new Error(`DeepSeek request failed: ${response.status} ${detail}`.trim())
+    }
+
+    const data = await response.json()
+    const content = data?.choices?.[0]?.message?.content
+    if (!content) {
+      throw new Error('DeepSeek returned an empty response')
+    }
+
+    let parsed
+    try {
+      parsed = JSON.parse(content)
+    } catch {
+      throw new Error('DeepSeek returned invalid JSON')
+    }
+
+    return {
+      raw: parsed,
+      normalized: normalizeEnrichmentResult(parsed),
+      model: data?.model || this.model,
+    }
+  }
+}