feat(usage): implement cost tracking backend and pricing configuration

- Add pricing constants with default rates for all providers
- Update localDb to support pricing configuration schema
- Add cost calculation logic to usageDb
- Add pricing management API endpoints
- Fix provider alias mapping for accurate cost lookups

🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/lib/localDb.js

@@ -41,7 +41,8 @@ const defaultData = {
   settings: {
     cloudEnabled: false,
     stickyRoundRobinLimit: 3
-  }
+  },
+  pricing: {} // NEW: pricing configuration
 };
 
 // Singleton instance
@@ -528,3 +529,158 @@ export async function isCloudEnabled() {
   return settings.cloudEnabled === true;
 }
 
+// ============ Pricing ============
+
+/**
+ * Get pricing configuration
+ * Returns merged user pricing with defaults
+ */
+export async function getPricing() {
+  const db = await getDb();
+  const userPricing = db.data.pricing || {};
+
+  // Import default pricing
+  const { getDefaultPricing } = await import("@/shared/constants/pricing.js");
+  const defaultPricing = getDefaultPricing();
+
+  // Merge user pricing with defaults
+  // User pricing overrides defaults for specific provider/model combinations
+  const mergedPricing = {};
+
+  for (const [provider, models] of Object.entries(defaultPricing)) {
+    mergedPricing[provider] = { ...models };
+
+    // Apply user overrides if they exist
+    if (userPricing[provider]) {
+      for (const [model, pricing] of Object.entries(userPricing[provider])) {
+        if (mergedPricing[provider][model]) {
+          mergedPricing[provider][model] = { ...mergedPricing[provider][model], ...pricing };
+        } else {
+          mergedPricing[provider][model] = pricing;
+        }
+      }
+    }
+  }
+
+  // Add any user-only pricing entries
+  for (const [provider, models] of Object.entries(userPricing)) {
+    if (!mergedPricing[provider]) {
+      mergedPricing[provider] = { ...models };
+    } else {
+      for (const [model, pricing] of Object.entries(models)) {
+        if (!mergedPricing[provider][model]) {
+          mergedPricing[provider][model] = pricing;
+        }
+      }
+    }
+  }
+
+  return mergedPricing;
+}
+
+/**
+ * Get pricing for a specific provider and model
+ */
+export async function getPricingForModel(provider, model) {
+  const pricing = await getPricing();
+
+  // Try direct lookup
+  if (pricing[provider] && pricing[provider][model]) {
+    return pricing[provider][model];
+  }
+
+  // Try mapping provider ID to alias
+  // We need to duplicate the mapping here or import it
+  // Since we can't easily import from open-sse, we'll implement the mapping locally
+  const PROVIDER_ID_TO_ALIAS = {
+    claude: "cc",
+    codex: "cx",
+    "gemini-cli": "gc",
+    qwen: "qw",
+    iflow: "if",
+    antigravity: "ag",
+    github: "gh",
+    openai: "openai",
+    anthropic: "anthropic",
+    gemini: "gemini",
+    openrouter: "openrouter",
+    glm: "glm",
+    kimi: "kimi",
+    minimax: "minimax",
+  };
+
+  const alias = PROVIDER_ID_TO_ALIAS[provider];
+  if (alias && pricing[alias]) {
+    return pricing[alias][model] || null;
+  }
+
+  return null;
+}
+
+/**
+ * Update pricing configuration
+ * @param {object} pricingData - New pricing data to merge
+ */
+export async function updatePricing(pricingData) {
+  const db = await getDb();
+
+  // Ensure pricing object exists
+  if (!db.data.pricing) {
+    db.data.pricing = {};
+  }
+
+  // Merge new pricing data
+  for (const [provider, models] of Object.entries(pricingData)) {
+    if (!db.data.pricing[provider]) {
+      db.data.pricing[provider] = {};
+    }
+
+    for (const [model, pricing] of Object.entries(models)) {
+      db.data.pricing[provider][model] = pricing;
+    }
+  }
+
+  await db.write();
+  return db.data.pricing;
+}
+
+/**
+ * Reset pricing to defaults for specific provider/model
+ * @param {string} provider - Provider ID
+ * @param {string} model - Model ID (optional, if not provided resets entire provider)
+ */
+export async function resetPricing(provider, model) {
+  const db = await getDb();
+
+  if (!db.data.pricing) {
+    db.data.pricing = {};
+  }
+
+  if (model) {
+    // Reset specific model
+    if (db.data.pricing[provider]) {
+      delete db.data.pricing[provider][model];
+      // Clean up empty provider objects
+      if (Object.keys(db.data.pricing[provider]).length === 0) {
+        delete db.data.pricing[provider];
+      }
+    }
+  } else {
+    // Reset entire provider
+    delete db.data.pricing[provider];
+  }
+
+  await db.write();
+  return db.data.pricing;
+}
+
+/**
+ * Reset all pricing to defaults
+ */
+export async function resetAllPricing() {
+  const db = await getDb();
+  db.data.pricing = {};
+  await db.write();
+  return db.data.pricing;
+}
+