deps: react-bootstrap 0.31 -> 2 (Bootstrap 5 CSS deferred as debt)

Removes the largest batch of React-19-blocking warnings: the 0.31
components (Grid, FormGroup, ControlLabel, Navbar.Header/Brand, Checkbox,
SafeAnchor) all leaned on legacy context / defaultProps.

29 files converted: Grid->Container, FormGroup/ControlLabel/FormControl/
HelpBlock -> Form.Group/Label/Control/Text, Checkbox -> Form.Check (label
as prop), bsStyle->variant (default->secondary), bsSize->size,
pull-right->float-end. Custom Col.js now re-exports v2's Col; custom
NavItem.js rewritten self-contained (no SafeAnchor/createChainedFunction);
Navigation.js drops react-bootstrap Navbar (raw markup anyway).

CSS stays on Bootstrap 4 (alexwine:bootstrap-4) for now: the BS4->5 jump
is entangled with the jQuery carousel/swipe + navbar-collapse and is
tracked as separate debt in UPGRADE.md. Only .form-label needed a shim
(forms.scss). Browser-verified home carousel+navbar, signup form + terms
checkbox, login form; REST smoke byte-identical.

imports/ui/components/Feedback/Feedback.js

@@ -6,7 +6,7 @@ import React, { Component } from 'react';
 import PropTypes from 'prop-types';
 import { Meteor } from 'meteor/meteor';
 import { withTranslation } from 'react-i18next';
-import { FormGroup, Button, FormControl } from 'react-bootstrap';
+import { Form, Button } from 'react-bootstrap';
 import { Bert } from 'meteor/themeteorchef:bert';
 import { withTracker } from 'meteor/react-meteor-data';
 import { isHome } from '/imports/ui/components/Utils/location';
@@ -82,7 +82,7 @@ class Feedback extends Component {
                   className="form card-body"
                   onSubmit={event => event.preventDefault()}
               >
-                <FormGroup controlId="formEmail">
+                <Form.Group controlId="formEmail">
                   <input
                       id={testId('emailInput')}
                       onChange={this.handleChange}
@@ -95,8 +95,8 @@ class Feedback extends Component {
                       defaultValue={disabled ? this.props.emailAddress : ''}
                       type="email"
                   />
-                </FormGroup>
-                <FormGroup
+                </Form.Group>
+                <Form.Group
                     controlId="formFeedback"
                 >
                   <textarea
@@ -107,9 +107,9 @@ class Feedback extends Component {
                       placeholder={t('Por favor, escribe aquí tu feedback...')}
                       rows="6"
                   />
-                  <FormControl.Feedback />
-                </FormGroup>
-                <Button type="submit" bsStyle="success" className="float-right" id={testId('sendFeedbackBtn')} >
+                  <Form.Control.Feedback />
+                </Form.Group>
+                <Button type="submit" variant="success" className="float-right" id={testId('sendFeedbackBtn')} >
                   {t('Enviar')}
                 </Button>
               </form>