ui: file manager read pills and Edit raw (v2.7.9)

The decoded view is a read-only field table, so pressing Edit there did
nothing (no readonly inputs to strip) and Save found nothing to write.

- Remove the redundant Read button: the Raw/Decoded pills already read
  the file, so they become explicit read actions — Read raw / Read
  decoded (Читать сырые данные / Декодировать).  They are buttons now
  so the server/card availability model disables them like the old Read
  button did.
- Edit raw (Редактировать сырые данные) always edits the hex view: from
  decoded (or with no content loaded yet) it switches back to raw and
  reads the file first; the decoded view stays read-only.
- Save/Cancel moved next to Edit raw (right-aligned group); the pills
  are inert and dimmed while editing (mode switching would discard
  unsaved changes).
- Tests: frontend/tests/fs_edit.test.js (skipRead, edit guard, decoded
  auto-switch ordering, read failure abort, cancel/reset); help EN/RU.

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "pysim-simple-server"
-version = "2.7.8"
+version = "2.7.9"
 description = "HTTP REST server wrapping pysim for the SIMple PWA"
 requires-python = ">=3.8"
 # pysim is a git-only dependency installed explicitly by setup.bat/setup.sh.