fix: expand language IDs, fix AtCoder submit, normalize logging (#353)

## Problem

Language version coverage was incomplete across all platforms, AtCoder
submit used a stale cookie fast-path that caused silent failures, and
raw
`vim.notify` calls throughout the codebase produced inconsistent or
missing `[cp.nvim]:` prefixes.

## Solution

Remove cookie persistence from AtCoder login/submit (always fresh
login),
increase the submit nav timeout to 40s, and switch to in-memory buffer
upload with the correct per-language extension from a full
`_LANGUAGE_ID_EXTENSION`
map covering all 116 AtCoder languages. Expand `LANGUAGE_VERSIONS` in
`constants.lua` with all AtCoder languages, 15 new CF languages with
full
version variants, and 50+ Kattis languages. Fix AtCoder `prolog` ID
(`6079`→`6081`, was Pony) and remove the non-existent `racket` entry.
Replace all raw `vim.notify` calls with `logger.log`. Simplify the
submit
language doc to point at `constants.lua` rather than maintaining a
static table.

lua/cp/submit.lua

@@ -78,7 +78,7 @@ function M.submit(opts)
 
   prompt_credentials(platform, function(creds)
     vim.cmd.update()
-    vim.notify('[cp.nvim] Submitting...', vim.log.levels.INFO)
+    logger.log('Submitting...', { level = vim.log.levels.INFO, override = true })
 
     require('cp.scraper').submit(
       platform,
@@ -89,7 +89,10 @@ function M.submit(opts)
       creds,
       function(ev)
         vim.schedule(function()
-          vim.notify('[cp.nvim] ' .. (STATUS_MSGS[ev.status] or ev.status), vim.log.levels.INFO)
+          logger.log(
+            STATUS_MSGS[ev.status] or ev.status,
+            { level = vim.log.levels.INFO, override = true }
+          )
         end)
       end,
       function(result)