Add single-ESP32S3 demo setup for presence detection

[Rudraa-25]

Simplified setup for running RuView with just ONE ESP32-S3 board:

• Basic presence detection (room occupancy)
• Motion detection
• Distance estimation

For full pose estimation (17 keypoints), breathing, and heart rate, 2+ nodes are recommended.

[ruvnet]

Thanks for the contribution — the single-node entry point is a real gap. A few issues to fix before this can land:

1. Flash offset 0x10000 is wrong. The repo's partition tables (partitions_display.csv, partitions_4mb.csv) put ota_0 at 0x20000. The README at firmware/esp32-csi-node/README.md was just corrected in fix: bug triage for #559, #561, #588 #590 (closes ESP32 CSI firmware README has inconsistent flash offset and provisioning path #561). Please use:

   0x0     bootloader.bin
   0x8000  partition-table.bin
   0xf000  ota_data_initial.bin
   0x20000 esp32-csi-node.bin
   

2. Release URL points at your fork. https://github.com/Rudraa-25/RuView/releases should be https://github.com/ruvnet/RuView/releases. Once a tagged firmware release exists upstream, the binaries the contributor expects (bootloader.bin, partition-table.bin, esp32-csi-node.bin, ota_data_initial.bin) are downloadable from there.

3. --source single flag. I don't see this flag in wifi-densepose-sensing-server's CLI. The closest existing one is --source esp32 or --source auto. Please verify the command runs end-to-end before merging.

4. requirements.txt for the sensing server. The sensing server is a Rust crate (cargo run -p wifi-densepose-sensing-server) — no Python deps needed. The pip install -r requirements.txt step should be removed.

5. Asset paths reference release/ (singular). The repo uses firmware/esp32-csi-node/release_bins/ (plural).

6. Location. Per CLAUDE.md, example code lives under /examples. Please move demo-single-esp32s3/ → examples/single-esp32s3/.

7. check_esp32.py location. Utility scripts live under /scripts per CLAUDE.md. If the script is specific to this example, keeping it inside examples/single-esp32s3/ is fine — just call that out in the README.

The intent is good and there's clearly a real audience for a single-node entry point. Happy to re-review once these are addressed.