fix: expand language IDs, fix AtCoder submit, normalize logging

Problem: AtCoder submit used a cookie fast-path that silently failed on
stale sessions; `_LANGUAGE_ID_EXTENSION` only covered 2 of 116 languages;
`LANGUAGE_VERSIONS` was incomplete for AtCoder, CF, and Kattis; AtCoder
`prolog` and `racket` entries had wrong IDs. Raw `vim.notify` calls
throughout bypassed `logger.log`, producing inconsistent or missing
`[cp.nvim]:` prefixes.

Solution: Remove cookie persistence from AtCoder login/submit — always
use a fresh login within a single session. Increase
`BROWSER_SUBMIT_NAV_TIMEOUT["atcoder"]` to 40s and switch to in-memory
buffer upload with the correct per-language extension. Expand
`LANGUAGE_VERSIONS` with all 116 AtCoder languages, 15 new CF languages
with full version variants (java8/21, kotlin 1.7/1.9/2.2, rust 2021/2024,
etc.), and 50+ Kattis languages. Fix AtCoder `prolog` ID (`6079`→`6081`,
was Pony) and remove non-existent `racket` entry. Replace all raw
`vim.notify` calls with `logger.log`.

lua/cp/pickers/fzf_lua.lua

@@ -1,3 +1,4 @@
+local logger = require('cp.log')
 local picker_utils = require('cp.pickers')
 
 local M = {}
@@ -9,10 +10,7 @@ local function contest_picker(platform, refresh, language)
   local contests = picker_utils.get_platform_contests(platform, refresh)
 
   if vim.tbl_isempty(contests) then
-    vim.notify(
-      ("No contests found for platform '%s'"):format(platform_display_name),
-      vim.log.levels.WARN
-    )
+    logger.log(("No contests found for platform '%s'"):format(platform_display_name), { level = vim.log.levels.WARN })
     return
   end