fix(launcher): localize image-missing placeholder + drop dead icons.lua

- markdown.lua: M.render now accepts an optional `t` 6th arg (ctx.t).
  When present, the image-missing fallback string is looked up via the
  new `image_missing_fmt` key in strings.lua. Callers without t (the
  launcher-test bytecopy) get the hardcoded English string verbatim,
  matching previous behavior.
- panels/detail.lua: both md.render call sites now thread ctx.t through.
- strings.lua: add image_missing_fmt = "[image missing: %s]".
- icons.lua: deleted. The v0.2.0 status-glyph helper was replaced by
  dep_glyph_* string keys in v0.3.0; grep confirmed no remaining refs.
- manifest.module: bump 0.3.2 -> 0.3.3.

strings.lua

@@ -22,4 +22,7 @@ return {
     no                    = "No",
     -- News entry default title
     news_default_title    = "News",
+    -- Markdown image-missing placeholder (rendered by markdown.lua when
+    -- engine.module.load_texture returns nil for an inline image source).
+    image_missing_fmt     = "[image missing: %s]",
 }