Add account profile password change flow

[TheSilkky]

Summary

• Add an authenticated account profile route with safe account metadata from GET /v1/account.
• Add a password-change form backed by POST /v1/account/password, with fixed safe error messages and explicit success-session wording.
• Refresh session account metadata after successful password change while keeping the current session active.
• Add profile navigation from the app shell and account menu.
• Update docs and tests for the implemented account profile/password flow.

Validation

• npm run typecheck
• npm run lint
• npm run test
• npm run build
• npm run test:e2e
• git diff --check

Security and Scope

• Frontend-only change; no backend implementation or deployment configuration changes.
• Uses documented account routes only: GET /v1/account and POST /v1/account/password.
• Passwords and request bodies are not logged, displayed, copied into route text, or persisted in session storage.
• No browser decryption, key unwrapping, recording, notification, emergency-response, admin-route, OAuth, JWT, billing, or password-reset-by-email behavior added.
• Password-change success keeps this browser session active and relies on the server to revoke other account sessions.

Closes #47

[TheSilkky]

@codex review

Please review this PR for correctness, security, scope control, tests, and
consistency with README.md, AGENTS.md, SECURITY.md, and relevant docs.

Focus on frontend route behavior, API client assumptions against
open-proofline/server, token handling, no secret logging, no browser decryption
or key unwrapping, Catalyst licensing boundaries, and validation results.

[chatgpt-codex-connector]

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