fix: dropdown overflow, popout-blocks-modal, non-image upload, residual mojibake

Several follow-up fixes to the post-3.24.0 soundboard rework that the
previous round missed, plus AlexT2803's three reports.

#5419 Soundboard popout breaks sound manager button
  (public/js/modules/app-media.js)
- _openSoundModal was short-circuiting for ALL tabs whenever the popout
  was active, which meant the admin Custom Sounds button (opens
  'manage') and the user's Assign-to-Events flow were both reachable
  only by first closing the popout. Now the early-flash-the-PiP path
  only fires when the requested tab is 'soundboard'; 'assign' and
  'manage' open the modal as usual.

#5417 Non-image files instantly uploaded
  (public/js/modules/app-media.js, app-ui.js, app-messages.js, style.css)
- Mirrors the existing image queue: non-image attachments now go into
  a new _fileQueue rendered as chips in the same image-queue-bar
  (filename + size + remove button), and are sent when the user hits
  Send. Hooks: _queueGeneralFile, _clearFileQueue, _flushFileQueue.
  Composer file-button, paste, and drag-drop all route through the
  queue. _flushFileQueue runs alongside _flushImageQueue at send time.
  PiP DM and threads still use the immediate upload path; can extend
  later if reported.

#5418 Dropdown overflow (Sound Manager → Assign to Events)
  (public/js/modules/app-media.js, public/css/style.css)
- Native <select> popups render outside the Haven window and can't
  be constrained. Added _enhanceSelectAsCustom which hides the native
  select and renders a div-based dropdown that lives inside the modal,
  flips above if needed, and scrolls when long. Wired into the five
  assign-* selects in _renderAssignTab; idempotent on re-render.

#5418 (cont.) Residual mojibake
  (public/index.html, public/js/modules/app-media.js)
- index.html TOS page: three em-dashes ('â€"' -> '—') and one
  '⚖️' restored from the cp1252 round-trip damage.
- app-media.js avatar save error: '❌' restored (the bytes for the
  c3a2c29dc592 mangling were too short to catch in the earlier sweep).

UTF-8 writes used Python with explicit BOM preservation per
AGENT_INSTRUCTIONS.md.

Author: ancsemi