[deckhouse-cli] add docs and htpasswd

[ldmonster]

Summary

New command: d8 tools htpasswd

A drop-in analog of Apache htpasswd that manages password files and hashes passwords without requiring the external htpasswd binary (apache2-utils / httpd-tools). Its primary purpose is generating a bcrypt hash for d8 iam user create / d8 iam user reset-password --password-hash, replacing the previous README recipe that shelled out to htpasswd -BinC 10 "" | cut -d: -f2 | tr -d '\n':

HASH="$(echo -n 'Test12345!' | d8 tools htpasswd -ni)"
d8 iam user reset-password test-user --password-hash "$HASH"

Full htpasswd parity:

• Operations: create (-c), delete (-D), verify (-v), print-to-stdout (-n); atomic file writes that preserve other entries and comments.
• Password input: batch (-b), stdin (-i), interactive prompt with confirmation.
• Algorithms: bcrypt (-B), apr1-MD5 (-m), SHA-256/512 crypt (-2/-5), plus the insecure legacy schemes DES crypt (-d), SHA-1 (-s), plaintext (-p). Flag bundling (-nbB) and digit flags (-2/-5) work as in htpasswd.
• Parameters: bcrypt -C cost, SHA -r rounds.

Two intentional, documented deviations from Apache htpasswd:

• Default is bcrypt at cost 10 (htpasswd defaults to apr1 at cost 5), so the output is strong and directly usable by d8 iam user.
• With -n and no username, the bare hash is printed (htpasswd always requires a username and prints user:hash) — exactly what --password-hash consumes.

bcrypt output uses the $2y$ identifier for byte-level parity with htpasswd.