Fix /clear command, places JSON parsing, stale AI prices, agent silent failures

[Copilot]

The clear history button was unusable on mobile, the agent quoted stale training prices even when live data was fetched, and the places search always failed silently when called via the agent.

Chat: replace clear button with /clear command

• Removed <a id="chat-clear"> from the chat template
• Intercept /clear in askLLM() before the fetch, call clearChatHistory() client-side

AI system prompt: current date + live data framing

• Injects time.Now() as Today's date is … so the model has temporal grounding
• Relabels RAG context block from "Recent context" → "Current context (live market data…)"
• Explicit instruction: "For prices: the data provided in context is current and live — quote it directly as the current price"

Places: fix JSON body parsing for agent tool calls

handleSearch/handleNearby read params via r.ParseForm() only. api.ExecuteTool sends a JSON body, so params were always empty → 400 → agent showed "unavailable". Extracted a shared helper:

func parseRequestParams(r *http.Request) func(string) string {
    r.ParseForm()
    var jsonBody map[string]interface{}
    if app.SendsJSON(r) {
        json.NewDecoder(r.Body).Decode(&jsonBody)
    }
    return func(key string) string {
        if v := r.Form.Get(key); v != "" { return v }
        if jsonBody != nil { if v, ok := jsonBody[key]; ok { return fmt.Sprintf("%v", v) } }
        return ""
    }
}

Both handlers now call parseRequestParams(r), handling both form (web UI) and JSON (agent/API).

Agent: log tool failures + stronger synthesiser prompt

• Tool errors are now logged with name, error, and truncated response body
• Synthesiser system prompt strengthened to explicitly forbid falling back to training data for prices/weather: "Do NOT use your training knowledge for current prices or live data — it will be outdated"

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