# Merge Request: SQLite Persistence, Latency Fallbacks, Thread-Safe KV Cache Lock, and Mobile UI Enhancements

## 📌 Overview
This Merge Request delivers critical enhancements to the **Kisan-Sathi** application to ensure thread safety, robust offline latency management, layout responsiveness, and clean system state resets.

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## 🚀 Key Enhancements

### 1. Latency & Timeout Fallbacks for local GGUF (`src/llm.py`)
To prevent the application from hanging on "Thinking..." when running local inference on slower CPU architectures (e.g., without AVX-512):
* **Model Loading Limit:** If the model loader (`init_llama_cpp()`) takes more than 35 seconds to load the GGUF file from disk, it automatically falls back to the mock backend.
* **Prefill Latency Limit:** If the initial prompt prefill (first token generation) takes more than 30 seconds, `llama_cpp` is disabled for subsequent prompts, falling back to the mock backend.
* **Optimized Thresholds:** Increased timeouts from 10s/15s to 30s/35s respectively, providing slow CPUs with sufficient headroom to process prompts successfully without premature timeouts.

### 2. Thread-Safety Lock to Prevent KV Cache Corruption (`src/llm.py`)
FastAPI serves requests concurrently, which previously caused simultaneous calls to the shared in-process `llama.cpp` model:
* **The Issue:** Simultaneous inference requests corrupted the model's KV cache, resulting in repetitive token loops (`आपका2आपका2`) or garbled strings (`नमस्ते4आपका`).
* **The Fix:** Implemented a global `threading.Lock` (`_model_lock`) inside `generate_llama_cpp()`. Access to the local GGUF model is serialized: subsequent calls wait until the streaming response of the active call completes.

### 3. Structured Digital Ledger Parser Fallback (`src/llm.py` & `src/ledger.py`)
* **The Issue:** When `llama_cpp` timed out during a ledger transaction parse query, it fell back to the mock chat backend. This returned a generic Hindi welcome message instead of valid JSON, crashing the ledger table.
* **The Fix:** Configured `generate_mock` to intercept structured extraction requests (checking for `"precise data extractor"` or `"json format"` system prompts) and parse fields like item, quantity, price, and type using regex rules to return a valid JSON payload.

### 4. "Start from Scratch" Reset Feature (`src/db.py`, `app.py`, `assets/index.html`)
Added a global reset capability to clear user registrations and start clean:
* **Database Backend:** Implemented `db.clear_all_data()` to clear `profile`, `calendars`, `tasks`, and `ledger` tables. Deletes local JSON/CSV backup files to prevent auto-restoring data.
* **FastAPI Server:** Exposed a new `@app.post("/api/reset")` endpoint.
* **Frontend UI:** Added a localized **🔄 Reset / सब साफ करें** button inside header controls, resetting state, clearing chat views, and displaying the onboarding panel.

### 5. Mobile Responsive UI CSS (`assets/index.html`)
* Added media queries (`@media (max-width: 600px)`) to adapt layouts for mobile views.
* Stacks header controls vertically, adjusts chat message widths to 95%, downsizes font/card metrics, and scales buttons/inputs for touch layouts.

### 6. Proactive Nudge Markdown Parser (`assets/index.html`)
* Fixed rendering of raw markdown asterisks (`**`) inside the seasonal nudge banner by routing the API response through the client-side `parseMarkdown()` function.

### 7. SQLite Database Migration & Cleanups
* Migrated local storage from JSON/CSV files to a native SQLite database (`kisan.db`), ensuring reliable offline persistence.
* Added support for individual transaction deletions and CSV exports.

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## 🛠️ Verification & Tests
All 6 core component unit tests pass successfully:
```bash
.venv\Scripts\python -m pytest
```
* **Output:** `6 passed in 8.85s`