Read feature, release workflow (v0.3.0)

- Read button (desktop and web): reads the tag now, bypassing the status
  cache, and puts its first link or text record into the input field so it
  can be copied to another tag. POST /api/read in the web version.
- Raw memory: every 4-byte page from page 0 (UID, lock bytes, CC, data) in
  hex and ASCII, collapsed by default.
- Content now shows the records and the note together (a locked tag showed
  only "read-only" before); read failures are flagged with read_failed
  instead of matching message text.
- .gitea/workflows/release.yml: on a v* tag, tests and clippy, then Linux
  (ubuntu-22.04, glibc 2.35) and Windows (MinGW cross-build) packages
  attached to the tag's release with its CHANGELOG.md section.
- README: reading, why the reader program runs on the reader's machine,
  releases.

README.md

@@ -1,6 +1,8 @@
 # NFC tag writer
 
-Programs NFC tags through a USB PC/SC reader such as the ACS ACR1252U-M1. Type a URL or some text, put a tag on the reader, press **Program**.
+Programs and reads NFC tags through a USB PC/SC reader such as the ACS ACR1252U-M1. Type a URL or some text, put a tag on the reader, press **Program**. Press **Read** to load a tag's link or text into the field, for example to copy it to another tag.
+
+Downloads for Windows and Linux: https://git.b4l.co.th/B4L/NFC/releases
 
 There are two ways to run it, with the same reader logic behind both:
 
@@ -16,6 +18,10 @@ There are two ways to run it, with the same reader logic behind both:
 - Supported tags: NTAG213, NTAG215, NTAG216 and MIFARE Ultralight / EV1 / C (NFC Forum Type 2). MIFARE Classic, DESFire and bank cards are recognised and refused with a message.
 - A write first empties the tag's NDEF message and writes its header last. If the tag is pulled away halfway, it ends up empty rather than holding broken data. After writing, the tag is read back and compared.
 
+## What it reads
+
+As soon as a tag is on the reader, the window shows its UID, chip type, memory use and content. **Read** reads the tag again and puts its first link or text into the input field. "Raw memory" lists every 4-byte page of the tag in hex and ASCII. Any card shows its UID; only Type 2 tags show content.
+
 ## Which reader it uses
 
 The program asks the operating system's smart-card service (PC/SC) for readers. Any PC/SC contactless reader should work, not only the ACR1252U.
@@ -53,6 +59,14 @@ sudo systemctl enable --now pcscd.socket
 
 Fedora: `sudo dnf install pkgconf pcsc-lite-devel pcsc-lite pcsc-lite-ccid`. Arch: `sudo pacman -S pkgconf pcsclite ccid`.
 
+## Why it runs on the machine with the reader
+
+Browsers cannot reach a USB smart-card reader: WebUSB blocks the smart-card device class, and Web NFC exists only in Chrome on Android. So the program that talks to the reader has to run on the computer the reader is plugged into. The web version is a convenience for that same computer; hosting it on a server would only reach the server's own USB ports.
+
+## Releases
+
+Push a tag `v*` (with a matching section in `CHANGELOG.md`): `.gitea/workflows/release.yml` tests, builds Linux and Windows x86_64 packages and attaches them to the tag's release.
+
 ## Tested
 
 | | Windows 11 | macOS | Linux |