feat: Add static changelog page

Adds a new static page accessible at /changelog to display site updates and changes manually.

- Creates a new Flask Blueprint in `routes/changelog.py` to handle the route logic.
- Registers the `changelog_bp` blueprint in `app.py`.
- Creates the corresponding template `templates/changelog/changelog.html` extending the base layout.
- Adds a link to the Changelog page in the main sidebar navigation in `templates/base.html`, using an archive icon for consistency.
- Applies basic card styling to the changelog page content for improved visual structure.

app.py

@@ -6,6 +6,7 @@ import jinja_partials
 from jinja2_fragments import render_block
 from decorators import validate_person, validate_topset, validate_workout
 from routes.auth import auth, get_person_by_id
+from routes.changelog import changelog_bp
 from extensions import db
 from utils import convert_str_to_date, generate_plot
 from flask_htmx import HTMX
@@ -32,8 +33,7 @@ def load_user(person_id):
     return get_person_by_id(person_id)
 
 app.register_blueprint(auth, url_prefix='/auth')
-
-
+app.register_blueprint(changelog_bp, url_prefix='/changelog')
 
 @app.after_request
 def response_minify(response):