feat: initial commit for stc32g12k128 wristband firmware

Docs/implementation_plan.md

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+# French Language & Addressable RGB LED (XL-2020RGBC-2812B) Implementation Plan
+
+## Goal Description
+Modify the wristband firmware to support **French-only UI display** and replace the discrete 3-pin LED control with the single-wire **addressable RGB LED (XL-2020RGBC-2812B)** protocol (WS2812B timing compatible).
+
+## User Review Required
+> [!IMPORTANT]
+> 1. **RGB LED (WS2812B) Control Pin**:
+>    The single-wire addressable RGB LED requires a high-speed bit-stream control pin (DIN).
+>    We will use the **P0.0 pin** (originally `LED_R` net) to drive the WS2812B DIN. P0.0 is already configured as a Push-Pull output.
+>    Pins `P2.7` (originally `LED_G`) and `P2.6` (originally `LED_B`) will be disabled (set to standard inputs or high logic).
+> 2. **French Translations**:
+>    All UI strings will be replaced with French equivalents formatted to fit the 120-pixel wide OLED screen (max 15 characters per line).
+
+## Open Questions
+None. The specifications are fully understood and mapping is direct.
+
+## Proposed Changes
+
+### Hardware / Drivers
+
+#### [MODIFY] [lcd_font.h](file:///c:/workfile/105/stc32g12k128/Drivers/lcd_font.h)
+No change needed for font, but we might include character translations if custom accent characters were needed. Since we use standard French without accents (like "ARME" instead of "ARMÉ") to avoid custom font complexity, no changes to `lcd_font.h` are required.
+
+### Application Logic
+
+#### [MODIFY] [main.c](file:///c:/workfile/105/stc32g12k128/App/main.c)
+1. **Redefine LED output**:
+   - Redefine `LED_R`, `LED_G`, `LED_B` as virtual/soft registers (`bit` variables). This allows the current logic in `Timer1_Isr` (which computes blink rates, colors, and vibrations) to remain 100% unchanged.
+2. **Implement WS2812B bit-bang driver**:
+   - Write a precise assembly/C bit-bang function `WS2812_Write24Bit(u8 g, u8 r, u8 b)` that drives `P0.0` (DIN) with the correct WS2812 high-speed timing (typical `T0H = 0.35us`, `T0L = 0.9us`, `T1H = 0.8us`, `T1L = 0.4us`).
+   - Implement `WS2812_Reset()` by holding DI low for `>80us` to latch data.
+3. **Trigger RGB updates**:
+   - At the end of `Timer1_Isr` (or during main loop), monitor changes to the virtual `LED_R`, `LED_G`, `LED_B` variables. If any changes are detected, output the 24-bit color to the WS2812 LED using the bit-bang driver.
+4. **French UI Translation**:
+   - Translate all string literals displayed on the screen into French (e.g. menu items, sensor default names, and system state texts).
+
+## Verification Plan
+
+### Automated Tests
+- Build code with Keil C251 to ensure 0 compile/link errors.
+
+### Manual Verification
+- Test using UART simulation commands:
+  - Verify that the simulated LED output in the serial log shows correct R/G/B status changes for different states.
+  - Verify that French strings are printed correctly on the screen simulator or display.
+  - Test pairing, confirmation, alarm, and SOS states to verify correct RGB LED color outputs.