feat: 實作個人自助指令群 profile/password/email/sessions/tokens/mfa（issue #11）

- lib/bear_cli/self_service.ex：六個子群組（profile show/set、password change、
  email change、sessions list/revoke/revoke-others、tokens list/create/revoke、
  mfa status/setup/disable/recovery-codes），對接 alterminal/bear#38 的
  /api/v1/profile* JSON API（PAT Bearer、任何有效帳號）
- 敏感輸入（密碼／驗證碼）互動提示讀取，非 TTY → 退出碼 2；
  一次性明文（PAT 明文、recovery codes）僅於成功當下輸出
- mfa setup：otpauth URI 本地生成 ASCII QR（新增 eqrcode 依賴），
  確認走 /mfa/setup/confirm（依 #38 實作）
- Api 模組新增 profile 系列端點與 429 分流；CLI 分派接上六個指令群組
- docs/commands.md §3.7 對齊 #38 實際 API（sessions 欄位、tokens create
  無 --scope、mfa setup/confirm、email 需重帶 new_email）；§7／§8／§9 與
  README 同步更新
- 測試 50 例（fake API 注入）：解析、輸出、退出碼、互動輸入、錯誤分流；
  mix precommit 全綠（114 passed）

mix.lock

@@ -1,4 +1,5 @@
 %{
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   "finch": {:hex, :finch, "0.23.0", "e3f9287ac25a8832f848b144c2b57346aac65b205e2e0629a52adfe6507fd837", [:mix], [{:mime, "~> 1.0 or ~> 2.0", [hex: :mime, repo: "hexpm", optional: false]}, {:mint, "~> 1.8", [hex: :mint, repo: "hexpm", optional: false]}, {:nimble_options, "~> 0.4 or ~> 1.0", [hex: :nimble_options, repo: "hexpm", optional: false]}, {:nimble_pool, "~> 1.1", [hex: :nimble_pool, repo: "hexpm", optional: false]}, {:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "80e58d3f936f57e3fdf404f83a3642897ae6d9fb642934e46da4d8fe761b99d5"},
   "hpax": {:hex, :hpax, "1.0.4", "777de5d433b0fbdc7c418159c8055910faa8047ffdb3d6b31098d2a46cd7685c", [:mix], [], "hexpm", "afc7cb142ebcc2d01ce7816190b98ce5dd49e799111b24249f3443d730f377ca"},
   "jason": {:hex, :jason, "1.4.5", "2e3a008590b0b8d7388c20293e9dcc9cf3e5d642fd2a114e4cbbb52e595d940a", [:mix], [{:decimal, "~> 1.0 or ~> 2.0 or ~> 3.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "b0c823996102bcd0239b3c2444eb00409b72f6a140c1950bc8b457d836b30684"},