feat(web): add Tavily as web search/extract/crawl backend (#1731)

Salvage of PR #1707 by @kshitijk4poor (cherry-picked with authorship preserved).

Adds Tavily as a third web backend alongside Firecrawl and Parallel, using the Tavily REST API via httpx.

- Backend selection via hermes tools → saved as web.backend in config.yaml
- All three tools supported: search, extract, crawl
- TAVILY_API_KEY in config registry, doctor, status, setup wizard
- 15 new Tavily tests + 9 backend selection tests + 5 config tests
- Backward compatible

Closes #1707

hermes_cli/config.py

@@ -379,6 +379,7 @@ ENV_VARS_BY_VERSION: Dict[int, List[str]] = {
     4: ["VOICE_TOOLS_OPENAI_KEY", "ELEVENLABS_API_KEY"],
     5: ["WHATSAPP_ENABLED", "WHATSAPP_MODE", "WHATSAPP_ALLOWED_USERS",
         "SLACK_BOT_TOKEN", "SLACK_APP_TOKEN", "SLACK_ALLOWED_USERS"],
+    10: ["TAVILY_API_KEY"],
 }
 
 # Required environment variables with metadata for migration prompts.
@@ -574,6 +575,14 @@ OPTIONAL_ENV_VARS = {
         "category": "tool",
         "advanced": True,
     },
+    "TAVILY_API_KEY": {
+        "description": "Tavily API key for AI-native web search, extract, and crawl",
+        "prompt": "Tavily API key",
+        "url": "https://app.tavily.com/home",
+        "tools": ["web_search", "web_extract", "web_crawl"],
+        "password": True,
+        "category": "tool",
+    },
     "BROWSERBASE_API_KEY": {
         "description": "Browserbase API key for cloud browser (optional — local browser works without this)",
         "prompt": "Browserbase API key",
@@ -1516,6 +1525,7 @@ def show_config():
         ("VOICE_TOOLS_OPENAI_KEY", "OpenAI (STT/TTS)"),
         ("PARALLEL_API_KEY", "Parallel"),
         ("FIRECRAWL_API_KEY", "Firecrawl"),
+        ("TAVILY_API_KEY", "Tavily"),
         ("BROWSERBASE_API_KEY", "Browserbase"),
         ("BROWSER_USE_API_KEY", "Browser Use"),
         ("FAL_KEY", "FAL"),
@@ -1664,7 +1674,8 @@ def set_config_value(key: str, value: str):
     # Check if it's an API key (goes to .env)
     api_keys = [
         'OPENROUTER_API_KEY', 'OPENAI_API_KEY', 'ANTHROPIC_API_KEY', 'VOICE_TOOLS_OPENAI_KEY',
-        'PARALLEL_API_KEY', 'FIRECRAWL_API_KEY', 'FIRECRAWL_API_URL', 'BROWSERBASE_API_KEY', 'BROWSERBASE_PROJECT_ID', 'BROWSER_USE_API_KEY',
+        'PARALLEL_API_KEY', 'FIRECRAWL_API_KEY', 'FIRECRAWL_API_URL', 'TAVILY_API_KEY',
+        'BROWSERBASE_API_KEY', 'BROWSERBASE_PROJECT_ID', 'BROWSER_USE_API_KEY',
         'FAL_KEY', 'TELEGRAM_BOT_TOKEN', 'DISCORD_BOT_TOKEN',
         'TERMINAL_SSH_HOST', 'TERMINAL_SSH_USER', 'TERMINAL_SSH_KEY',
         'SUDO_PASSWORD', 'SLACK_BOT_TOKEN', 'SLACK_APP_TOKEN',