Add VoiceNotes firmware and CDM customer service SQL project

VoiceNotes is an Arduino sketch for the Waveshare ESP32-C6-LCD-0.85 that
records meetings and voice memos to microSD and turns them into notes:

- Records 16 kHz mono WAV (up to 4 h) from the ES7210 dual mics, with a
  boosted preamp and soft-limited digital gain
- Transcribes via an OpenAI-compatible speech-to-text API in ~10 min parts
  cut at quiet points, with retries and resume after failures
- Summarizes the transcript with Claude into meeting notes (decisions,
  action items, topics with timestamps), streamed to and from the card
- Copies the notes to Nextcloud over WebDAV
- Shows recording/processing state on the 0.85" LCD and the LED ring
- Works around the board's SD card failing multi-sector reads

Credentials live in VoiceNotes/secrets.h, which is git-ignored; see
secrets.example.h.

Also adds the Microsoft CDM customer service SQL implementation (DDL,
sample data, reporting queries and docs). Its README is renamed to
CDM_README.md so the repository README stays at the top level.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

VoiceNotes/app_state.h

@@ -0,0 +1,46 @@
+// State shared between the main loop, the audio task and the network task.
+#pragma once
+#include <Arduino.h>
+#include <freertos/FreeRTOS.h>
+#include <freertos/semphr.h>
+
+enum AppState : uint8_t {
+  ST_BOOT,
+  ST_NO_SD,
+  ST_IDLE,
+  ST_RECORDING,
+  ST_SAVED,
+  ST_UPLOADING,     // sending the WAV to the speech-to-text service
+  ST_TRANSCRIBING,  // waiting for / receiving the transcript
+  ST_SUMMARIZING,   // Claude is writing the notes
+  ST_SYNCING,       // copying the notes to Nextcloud
+  ST_DONE,
+  ST_ERROR,
+};
+
+struct AppStatus {
+  volatile AppState state = ST_BOOT;
+  volatile uint32_t stateSince = 0;     // millis() when the state was entered
+  volatile uint8_t progress = 0;        // 0-100 for ST_UPLOADING
+  volatile uint32_t received = 0;       // bytes of transcript / summary received
+  volatile float micLevel = 0;          // 0..1, updated by the audio task
+  volatile uint32_t recordedBytes = 0;  // PCM bytes in the current recording
+  volatile uint32_t droppedBytes = 0;   // audio lost because the SD card stalled
+  volatile uint32_t maxSeconds = 0;     // recording limit, from config and free space
+  volatile uint8_t partIndex = 0;       // transcription part being processed (1-based)
+  volatile uint8_t partCount = 0;       // estimated number of parts
+  char lastRecording[64] = "";          // full path of the newest .wav
+  char detail[96] = "";                 // file name / error text shown on screen
+};
+
+extern AppStatus app;
+
+// The LCD and the microSD share one SPI bus; anything touching either must hold this.
+extern SemaphoreHandle_t spiMutex;
+struct SpiLock {
+  SpiLock() { xSemaphoreTake(spiMutex, portMAX_DELAY); }
+  ~SpiLock() { xSemaphoreGive(spiMutex); }
+};
+
+void setState(AppState s, const char *detail = nullptr);
+bool timeIsValid();