docs: add first-person development blog post draft

[evandhoffman]

Summary

Adds docs/blog_post_birdvision_development.md — a first-person, origin-story
blog post draft fleshed out from the notes I had been writing.

It extends the narrative through the full arc:

• Origin + desktop proof-of-concept — the "smart scope" idea, the old
  gaming PC wiped to Ubuntu, YOLOv8 + BioCLIP, eBird priors, OAuth, the
  ensemble/eval/Gemma side-quests.
• Pi backyard mode — the Hailo-8 kit, the camcorder → HDMI → Cam Link 4K
  capture path, compiling YOLOv8n and a fine-tuned EfficientNet-V2-S to HEF
  (the Blue Jay training-data bug, the dynamo=False / NHWC calibration
  gotchas), the real-time pipeline, and the Touch Display framebuffer overlay.
• Phone sidecar mode — phone-as-camera over WebSocket/HTTPS, the Caddy
  reverse proxy, file uploads, single-client guard, and zoom controls.

Notes

• Kept in the author's casual first-person voice.
• Intentionally separate from the existing, more technical
  blog_post_birdvision_pi.md draft — that one is left untouched.
• Docs-only change; no code, tests, or config touched.