[AB-3423] Fix user authentication bug

[igzard]

Summary

This PR implements the changes requested in YouTrack ticket AB-3423.

Ticket Summary: Fix user authentication bug

Description

Fix user authentication bug

The login form is not validating email addresses properly. Users can submit invalid email formats and this causes errors in the backend.

Requirements:

• Add proper email validation to the frontend
• Ensure backend also validates email format
• Show user-friendly error messages
• Add tests for email validation

Generated Implementation

╭────────────────────────────────────────────────────────────────────╮
│ │
│ Configuration Error │
│ │
│ The configuration file at /root/.claude.json contains invalid │
│ JSON. │
│ │
│ Unterminated string in JSON at position 29728 (line 301 column 7) │
│ │
│ Choose an option: │
│ ❯ 1. Exit and fix manually │
│ 2. Reset with default configuration │
│ │
╰────────────────────────────────────────────────────────────────────╯

�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[GError: Raw mode is not supported on the current process.stdin, which Ink uses as input stream by default.
Read about how to prevent this error on https://github.com/vadimdemedes/ink/#israwmodesupported
at handleSetRawMode (file:///usr/local/lib/node_modules/@anthropic-ai/claude-code/cli.js:714:3853)
at file:///usr/local/lib/node_modules/@anthropic-ai/claude-code/cli.js:723:259
at jF (file:///usr/local/lib/node_modules/@anthropic-ai/claude-code/cli.js:67:21530)
at jX (file:///usr/local/lib/node_modules/@anthropic-ai/claude-code/cli.js:67:41141)
at file:///usr/local/lib/node_modules/@anthropic-ai/claude-code/cli.js:67:39313
at $l1 (file:///usr/local/lib/node_modules/@anthropic-ai/claude-code/cli.js:61:78952)
at Immediate.Cl1 [as _onImmediate] (file:///usr/local/lib/node_modules/@anthropic-ai/claude-code/cli.js:61:79371)
at process.processImmediate (node:internal/timers:485:21)
╭────────────────────────────────────────────────────────────────────╮
│ │
│ Configuration Error │
│ │
│ The configuration file at /root/.claude.json contains invalid │
│ JSON. │
│ │
│ Unterminated string in JSON at position 29728 (line 301 column 7) │
│ │
│ Choose an option: │
│ ❯ 1. Exit and fix manually │
│ 2. Reset with default configuration │
│ │
╰────────────────────────────────────────────────────────────────────╯

�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[G
ERROR Raw mode is not supported on the current process.stdin, which Ink uses
as input stream by default.
Read about how to prevent this error on
https://github.com/vadimdemedes/ink/#israwmodesupported

• Read about how to prevent this error on
  https://github.com/vadimdemedes/ink/#israwmodesupported
  -handleSetRawM (file:///usr/local/lib/node_modules/@anthropic-ai/claude-code/c
  ode li.js:714:3853)

(file:///usr/local/lib/node_modules/@anthropic-ai/claude-code/cli.js:723:259)

-jF (file:///usr/local/lib/node_modules/@anthropic-ai/claude-code/cli.js:67:21
530)
-jX (file:///usr/local/lib/node_modules/@anthropic-ai/claude-code/cli.js:67:41
141)

• (file:///usr/local/lib/node_modules/@anthropic-ai/claude-code/cli.js:67:3931

-$l1 (file:///usr/local/lib/node_modules/@anthropic-ai/claude-code/cli.js:61:7
8952)
-Immediate.C (file:///usr/local/lib/node_modules/@anthropic-ai/claude-code/cli
1 .js:61:79371)

• process.processImmediate (node:internal/timers:485:21)

Error: Raw mode is not supported on the current process.stdin, which Ink uses as input stream by default.
Read about how to prevent this error on https://github.com/vadimdemedes/ink/#israwmodesupported
at handleSetRawMode (file:///usr/local/lib/node_modules/@anthropic-ai/claude-code/cli.js:714:3853)
at file:///usr/local/lib/node_modules/@anthropic-ai/claude-code/cli.js:723:259
at jF (file:///usr/local/lib/node_modules/@anthropic-ai/claude-code/cli.js:67:21530)
at jX (file:///usr/local/lib/node_modules/@anthropic-ai/claude-code/cli.js:67:41141)
at file:///usr/local/lib/node_modules/@anthropic-ai/claude-code/cli.js:67:39313
at $l1 (file:///usr/local/lib/node_modules/@anthropic-ai/claude-code/cli.js:61:78952)
at Immediate.Cl1 [as _onImmediate] (file:///usr/local/lib/node_modules/@anthropic-ai/claude-code/cli.js:61:79371)
at process.processImmediate (node:internal/timers:485:21)

Checklist

• Code has been tested
• Documentation has been updated if necessary
• All tests pass
• Code follows project style guidelines

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This PR was automatically generated by Billy AI Dev Bot
YouTrack Ticket: AB-3423