Summary

Yes, there is a limit to the number of tactics cards you can hold in your hand.

• At the start of the game, your tactics card hand limit is 5.
• You must discard down to this limit at the end of your turn.
• You can increase this limit by advancing on the civilization track.

This is stated in the Core Rulebook, page 14:

"At the start of the game, you have a hand limit of 5 tactics cards. You must discard down to this limit at the end of your turn. You can increase this limit by advancing on the civilization track."

Additionally, the Appendix, page 25 clarifies:

"Players do not have to discard down to their tactics card hand limit until the end of their turn."

No limit is specified for other card types in the provided context.

Source: Core Rulebook, page 14; Appendix, page 25.

Sources:

• Core Rulebook (pp. 14, 27, 28, 3, 5)
• Appendix (pp. 22, 23, 25, 26)