Feature/save search filter: Add saving search filters ability

[itspavant]

PR Checklist

• Follows single-purpose principle
• Tests pass locally
• Documentation updated

What does this PR do?

Implements Saved Filters (saved searches) for tix.

Features added

• tix filter save <name> <filter_params> → Save a filter by name (e.g., priority, tag, completed/active).
• tix filter list → List all saved filters with their parameters.
• tix filter apply --saved <name> → Apply a saved filter.
• tix filter apply <filter_params> → Apply a filter directly without saving.
• Saved filters are stored in ~/.tix/filters.json.
• Overwriting filters supported via --force.

Related Issue

Closes #67

Type of change

• Bug fix
• New feature
• Configuration
• Documentation

How to test

# Save a filter named "work" for high-priority tasks tagged "work"
tix filter save work -t work -p high

# Save filter for completed tasks
tix filter save done-only --completed

# Overwrite an existing filter
tix filter save work -t work -p medium --force

# List all saved filters
tix filter list

# Apply saved filter
tix filter apply --saved work

# Apply filter directly without saving
tix filter apply -p high -t urgent

Additional Notes

• Added usage guidelines in readme regarding same
• This contribution is a part of Hacktoberfest

[itspavant]

Hiiiii @Valentin-v-Todorov

Kindly please review the PR, and let me know if you need any more modifications.

[Valentin-v-Todorov]

@itspavant LGTM !

🥇 Great job implementing the filters feature !! 🥇

There are just a few conflicts , please fix them and we can merge !