Fix Slack and MS Teams notifiers not reading URL from dashboard config

[dc-larsen]

Summary

• SlackNotifier and MSTeamsNotifier both read self.config.get('webhook_url') but notifications.yaml defines param names as slack_webhook_url and msteams_webhook_url. Same class of bug as Fix webhook notifier not reading URL from dashboard config #34.
• MS Teams was also missing its auto-enablement block in NotificationManager.load_from_config(), so it couldn't load via dashboard config or env var at all.
• Env var fallback paths were unaffected.

Root cause

Notifier	Config key used	Param name in notifications.yaml
SlackNotifier	self.config.get('webhook_url')	slack_webhook_url
MSTeamsNotifier	self.config.get('webhook_url')	msteams_webhook_url

Additionally, the manager's load_from_config() had enablement blocks for slack, webhook, ms_sentinel, jira, sumologic, and github_pr, but none for msteams.

Changes

• slack_notifier.py: self.config.get('webhook_url') -> self.config.get('slack_webhook_url')
• ms_teams_notifier.py: self.config.get('webhook_url') -> self.config.get('msteams_webhook_url')
• manager.py: Added msteams auto-enablement block + imported get_msteams_webhook_url

Reproduction

from socket_basics.core.notification.slack_notifier import SlackNotifier
from socket_basics.core.notification.ms_teams_notifier import MSTeamsNotifier

# Before fix: both return empty/falsy
s = SlackNotifier({"slack_webhook_url": "https://hooks.slack.com/test"})
print(s.webhook_url)  # Before: '' | After: 'https://hooks.slack.com/test'

m = MSTeamsNotifier({"msteams_webhook_url": "https://outlook.office.com/webhook/test"})
print(m.webhook_url)  # Before: '' | After: 'https://outlook.office.com/webhook/test'

Testing

• 7 new tests in tests/test_slack_notifier_params.py (direct params, env var, precedence, manager flow)
• 7 new tests in tests/test_msteams_notifier_params.py (direct params, env var, precedence, manager flow)
• Full suite: 112/112 passed

Context

Found while testing v1.1.1 for a customer. The webhook version of this bug was fixed in #34. This PR completes the fix across all webhook-based notifiers.