Add READMEs, docs, and LICENSE for publishing

- LICENSE: MIT, with attribution notes for the vendored qrcode/epaper_fonts/
  dns_server code and the epd7in3e driver's transcription of Waveshare's
  register sequence.
- Top-level README.md: project overview, hardware list, quick-start
  pointing at firmware/ and server/, repo layout, license, Claude Code
  attribution.
- firmware/README.md: full rewrite (was still the stock ESP-IDF captive
  portal example's README) -- build/flash instructions, Kconfig reference
  table, first-boot walkthrough, and how to reset to provisioning mode via
  NVS erase (the only way in right now; a proper reconfigure trigger is a
  future addition).
- docs/hardware.md: wiring table + parts list + strapping-pin/SPI-speed notes.
- docs/architecture.md: sequence diagram and walkthrough of the full
  provision -> connect -> fetch -> display -> sleep cycle, plus the
  reasoning behind doing image processing server-side and reusing Immich's
  face detection instead of bundling a detector.
- server/README.md: fixed stale endpoint docs (missing GET /frame/config,
  POST /api/config still describing removed immich_url/api_key fields).

docs/hardware.md

@@ -0,0 +1,52 @@
+# Hardware
+
+## Parts
+
+- An ESP32-C6 dev board (e.g. ESP32-C6-DevKitC-1). Needs 8MB flash --
+  see [`firmware/sdkconfig.defaults`](../firmware/sdkconfig.defaults) and
+  [`firmware/partitions.csv`](../firmware/partitions.csv) if yours differs.
+- [Waveshare 7.3" E Ink Spectra 6 (E6) panel](https://www.waveshare.com/7.3inch-e-paper-hat-e.htm) --
+  800x480, 6-color, SPI.
+- A USB cable for flashing/power.
+
+## Wiring
+
+The panel connects over SPI plus three control lines (data/command, reset,
+busy). Defaults below match the reference build and are set in
+[`firmware/components/epd7in3e/Kconfig`](../firmware/components/epd7in3e/Kconfig) --
+override via `idf.py menuconfig` under **E-Paper Display (epd7in3e)
+Configuration** if your wiring differs.
+
+| Panel pin | ESP32-C6 GPIO | Kconfig option    |
+| --------- | ------------- | ----------------- |
+| CLK       | 20            | `EPD_PIN_CLK`      |
+| DIN       | 19            | `EPD_PIN_MOSI`     |
+| CS        | 18            | `EPD_PIN_CS`       |
+| DC        | 9             | `EPD_PIN_DC`       |
+| RST       | 10            | `EPD_PIN_RST`      |
+| BUSY      | 11            | `EPD_PIN_BUSY`     |
+| VCC       | 3.3V          | --                 |
+| GND       | GND           | --                 |
+
+A couple of things worth knowing if you pick different pins:
+
+- **Avoid the ESP32-C6's strapping pins** (GPIO 4, 5, 8, 9, 15) and the
+  USB-JTAG pins (12, 13) where possible -- strapping pins are sampled at
+  reset to select boot mode. The reference wiring above already uses
+  GPIO9 for DC, which *is* a strapping pin; it's only sampled during
+  power-on/reset, so it's safe once the app is running, but if
+  flashing/boot ever misbehaves on your board, check whether the panel is
+  pulling that line low during reset.
+- The panel's SPI interface is rated well above the firmware's default
+  4MHz clock (`EPD_SPI_CLOCK_HZ`), but breadboard/dupont-wire connections
+  are often unreliable much past a few MHz. Raise it once your physical
+  wiring is confirmed solid.
+
+## Power
+
+The device spends nearly all its time in deep sleep, waking briefly once
+an hour (configurable, see the server's web UI) to fetch and display a
+photo. A full-color refresh on this panel takes 15-30+ seconds and draws
+more current than deep sleep by a wide margin -- expect battery life (if
+not running from USB power) to be dominated by refresh frequency, not
+sleep current.