Before answering, some clarification of terms.
- chord progression: Any sequence of two or more chords
- measure: A set number of musical pulses
- phrase: A complete musical idea, typically ending with a cadence
- cadence: A special chord progression creating a sense of pause or ending
Chord progressions, measures, and phrases all can act independently of each other. A phrase can span one or more measures, including partial measures, so a cadence can occur and the end of a measure, or anywhere at the beginning or middle as well. It's fine for a cadence to occur across the boundaries of a measure, such as the V chord at the end of one measure and the I chord at the beginning of the next.
A chord progression corresponding to a musical phrase, would end in a cadence. Given the above relationship between phrases and measures, a chord progression can begin or end at any point within a measure. "Chord progression", being a general term, could encompass just part of a phrase, a complete phrase, or multiple phrases — even an entire piece could be discussed in terms of its chord progression.
Regarding perfect cadences
A perfect cadence is a V chord followed by a I chord, but a V chord followed by a I chord is not necessarily a perfect cadence. A V chord followed by a I chord at the end of a phrase is a perfect cadence, but V-I chords can occur anywhere within a phrase.
This is true for any set of cadential chords. They can occur anywhere within a phrase; it's only at the end of a phrase that they form a cadence.