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/pickers/fzf_lua.lua

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