feat: initial model catalog with 196 models across 39 providers

Community-maintained TOML catalog for LibreFang. New models can be added
via PR without requiring a LibreFang binary release.

Includes validation script, bilingual docs, and GitHub templates.

CONTRIBUTING.md

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+# Contributing to LibreFang Model Catalog
+
+Thank you for helping keep the model catalog up to date! This guide explains how to add or update model entries.
+
+## How to Add a New Model
+
+### 1. Fork & Clone
+
+```bash
+git clone https://github.com/<your-fork>/model-catalog.git
+cd model-catalog
+```
+
+### 2. Find the Right Provider File
+
+Each provider has its own file in `providers/`. For example:
+- OpenAI models go in `providers/openai.toml`
+- Anthropic models go in `providers/anthropic.toml`
+
+If the provider doesn't exist yet, create a new file (e.g. `providers/newprovider.toml`) with the `[provider]` section and your `[[models]]` entries.
+
+### 3. Add Your Model Entry
+
+Append a `[[models]]` block to the provider file:
+
+```toml
+[[models]]
+id = "new-model-id"              # The exact API model ID
+display_name = "New Model Name"  # Human-readable name
+tier = "smart"                   # frontier | smart | balanced | fast | local
+context_window = 128000
+max_output_tokens = 16384
+input_cost_per_m = 2.50          # USD per million input tokens
+output_cost_per_m = 10.0         # USD per million output tokens
+supports_tools = true
+supports_vision = false
+supports_streaming = true
+aliases = []                     # Optional short names
+```
+
+### 4. Validate
+
+```bash
+python scripts/validate.py
+```
+
+This checks:
+- All TOML files parse correctly
+- Required fields are present
+- Tier values are valid
+- Costs are non-negative
+- No duplicate model IDs
+
+### 5. Submit a Pull Request
+
+Push your branch and open a PR. The PR template will guide you through the checklist.
+
+## Where to Find Model Information
+
+- **OpenAI**: https://openai.com/pricing
+- **Anthropic**: https://docs.anthropic.com/en/docs/about-claude/models
+- **Google Gemini**: https://ai.google.dev/pricing
+- **DeepSeek**: https://platform.deepseek.com/api-docs/pricing
+- **Mistral**: https://mistral.ai/technology/#pricing
+- **Groq**: https://wow.groq.com/
+- **xAI**: https://docs.x.ai/docs
+- **Cohere**: https://cohere.com/pricing
+- **Together**: https://www.together.ai/pricing
+- **Fireworks**: https://fireworks.ai/pricing
+- **Perplexity**: https://docs.perplexity.ai/guides/pricing
+
+## Tier Definitions
+
+| Tier | Description | Examples |
+|------|-------------|----------|
+| `frontier` | Most capable, cutting-edge | Claude Opus, GPT-4.1, Gemini 2.5 Pro |
+| `smart` | Smart and cost-effective | Claude Sonnet, GPT-4o, Gemini 2.5 Flash |
+| `balanced` | Balanced speed and cost | GPT-4.1 Mini, Llama 3.3 70B |
+| `fast` | Fastest, cheapest | GPT-4o Mini, Claude Haiku, Gemma 2 9B |
+| `local` | Local models, zero cost | Ollama, vLLM, LM Studio |
+
+## Guidelines
+
+- **Pricing must be in USD per million tokens** -- convert from other units if needed
+- **Use the exact model ID** that the provider's API expects
+- **Don't guess** -- only add data you can verify from official sources
+- **One provider per file** -- don't mix providers in a single TOML file
+- **Keep aliases short** -- 1-3 word abbreviations that users would naturally type
+
+---
+
+# 贡献指南
+
+感谢您帮助维护模型目录！以下是添加或更新模型条目的方法。
+
+## 如何添加新模型
+
+1. Fork 并克隆此仓库
+2. 在 `providers/` 目录中找到对应的提供商文件
+3. 添加 `[[models]]` 条目（参考上方英文模板）
+4. 运行 `python scripts/validate.py` 验证
+5. 提交 Pull Request
+
+## 定价说明
+
+- 所有价格均以 **美元/百万 tokens** 为单位
+- 免费模型和本地模型的价格为 `0.0`
+- 请从官方定价页面获取准确数据