[wallet/symbol/mobile] fix: Multisig Account Modification confirmation dialog text

[OlegMakarenko]

Problem:

• The multisig confirmation dialog always shows the title "Confirm Multisig Creation", even when the user is modifying an existing multisig account — this doesn't match the "Modify Multisig Account" screen and is misleading.
• The dialog body also reuses the create-specific text ("You are about to create a multisig account at %{address}...") during the modify flow, which is inaccurate since no new account is being created.
• Root cause: both the create and modify flows reuse the same localization key (s_multisig_create_dialog_confirm_title), which is only correct for the create flow.

Solution:

• Added a separate modify-flow string for the confirmation dialog title and body, distinct from the create-flow strings.
• Updated the confirmation dialog to select the create vs. modify copy based on which flow triggered it.

Resolved: #2397

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.37%. Comparing base (f26cf7f) to head (3523bf6).

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #2452      +/-   ##
==========================================
- Coverage   95.59%   95.37%   -0.23%     
==========================================
  Files         716      679      -37     
  Lines       53377    50606    -2771     
  Branches     1403     1404       +1     
==========================================
- Hits        51027    48265    -2762     
+ Misses       2291     2284       -7     
+ Partials       59       57       -2     

Flag	Coverage Δ
explorer-puller	?
explorer-rest	?
wallet-mobile-symbol	94.17% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...ile/src/screens/multisig/ModifyMultisigAccount.jsx	97.84% <100.00%> (ø)

... and 38 files with indirect coverage changes

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[Wayonb]

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