How can someone integrate the Buddhist philosophy on life's purpose into daily life?

The idea of "purpose" is a concept produced by our small minds. It is a construct, a trap, and an impediment toward liberation. Freedom is non-purpose. Nirvana has no meaning. Enlightenment is not something we work towards. It isn't something we cultivate or develop. Becoming is the opposite of being. See the following:

A monk asked Dasui, "When the kalpa fire flares up and the great cosmos is destroyed, I wonder, will "it" perish, or will it not perish?" Dasui said, "It will perish." The monk said, "Then it will be gone with the other?" Dasui said, "It will be gone with the other."

Blocked by the double barrier, The monk asked from the heart of the kalpa fire. Wonderful the words, "It will be gone with the other." Thousands of miles he wandered in vain, seeking a master.

You are in the heart of the kalpa fire. Everything is burning, burning. Wonderful, so wonderful the words - it will all be gone.

It all will be gone. What purpose is there to fulfill?

It is impossible to seek escape from suffering and still lead a normal day to day life because escape from suffering requires sincerity in thoughts and deeds towards the liberation goal...you must give up whatever you believe to own.
Having said that you can still try to move towards the goal of life while still leading normal life. First you must recognise Buddha as your guide , someone for whom you tremendous respect. Next you must do whatever you do as something only to reduce , remove the suffering... it can be by sharing the teachings of Buddha or by making products which remove or reduce the suffering of people ... or by protecting the weak and poor .... or by doings things which increase your merit for getting liberated... There is long list of things you can do to increase merit ...
Serve the people and encourage others to serve as well. People are best served by protecting the compassionate and being yourself compassionate... These traits will slowly lead you towards the goal of liberation.

I think that people, and especially lay-people, have social relations -- they are and they have children, parents, friends, employers, employees, teachers, students, spouses. And people inherit a moral obligation to be a good friend, a good parent, a good child, a good employer, and so on -- see DN 31.

Some people decide, "This house-holder's life is confining", and go forth (with their parent's permission) -- where they have fewer of these social obligations, though a lot of Sangha rules.

If you don't meet obligations -- if you're a bad parent, for example, or a bad friend -- then suffering ensues.

There's a sutta, What is the Purpose? (AN11.1) which begins,

So I have heard. At one time the Buddha was staying near Sāvatthī in Jeta’s Grove, Anāthapiṇḍika’s monastery.

Then Venerable Ānanda went up to the Buddha, bowed, sat down to one side, and said to him:

“Sir, what’s the purpose and benefit of skillful ethics?”

“Ānanda, having no regrets is the purpose and benefit of skillful ethics.”

Perhaps that's similar for laypeople as it is for monks.

As i learned Buddhis texts i had these thoughts: 'Many things are valued by people such as wealth & posessions and these go out of fashion. There are other things valued by people such as wisdom, integrity, hard work and reliability, these do not go out of fashion and are qualities found in people. Many people seek out good qualities in other people but few undertake to develop those qualities in themselves, one who would develop these qualities would be considered to be a gem of a person."

Therefore if we want to create any meaningful value we have no choice but to develop ourselves because if we don't have good in us then we won't be able to win good friends and we can't develop good in other people.

It takes a certain amount of development to see the final goal of Buddhist training but there is a goal and work is finite, once the work is done there is then nothing left for the Arahant to accomplish.

Daily life integration can be about getting into meditation, supporting others and restraining one's own bad traits.

I trust Buddha's teaching is practical in life, not just theory. Planning and liberation has no contradiction.

layperson with no dhamma knowledge, planned with attachment to the expected outcome.

Planning with expected outcome, attached to the expected outcome, and if the expected outcome is not happening, suffering follow us. This type of planning do not leads to liberation. Hence, without attachment to the expected outcome is way for liberation when we plan and when we set goal, thus suffering will not follow us.

The essence of dukkha (suffering) is clash, conflict, discord, disharmony - of some kind, whether inner conflict in one person's mind or outer conflict between persons or groups of people.

The opposite of that is happiness, whose essence is peace and harmony.

A lay person could make meaningful contribution to society and make progress towards liberation from samsara by dedicating his or her life to reducing the causes of suffering and creating causes of happiness.

Specifically, reducing, preventing, reconciling inner and outer conflicts and helping with implementation of behaviors that lead to peace and harmony.

For example, a professional peacemaker/negotiator in armed conflicts is someone who resolves external conflicts. Resolving external conflicts he or she removes causes of suffering. Making peace he or she creates causes of happiness.

You can come up with more ideas like this. A psychologist reduces suffering that happens due to inner conflicts. A teacher reduces suffering that happens due to ignorance and confusion.

Various professions work in different areas and have different level of influence: some work at individual level and some work with large groups of people.

The important thing to realize is what I started my answer with. As long as your job is reducing causes of suffering such as conflicts, clashes, greed, hatred, confusion, ignorance - you will both make a nice contribution to society and make progress on the Path.

When a person pursues a goal, there are two things to be considered:

• The pursuit, which exists only in the past and the future. Pursuit implies a belief that something can be other than it is; it implies an evaluation of the world into the desirable and the undesirable.
• The act of doing, which exists only in the present moment. We do, and inevitably we move the world a bit this way or that way.

Now, most (lay) people understand the first. They set their goals and their plans and they forge ahead, muddling through as best they can when they run into moral quandaries. Most (monastic) people understand the second. They understand that every act they make reverberates in karma, so they take great care to tread the middle path. It's a rare and difficult effort to try and grasp both. But it's not impossible.

My general approach is to adopt a 'means justifies the end' model (note the inversion of the old Machiavellian trope...). If we set goals and make plans, we must remember that the goal is no better (and perhaps worse) than the worst thing we must do to achieve it. If we reach for the best thing we can imagine, but must kill someone to make it happen, then (ipso facto) the goal (the best thing we can imagine) is no better than murder, and thus not worth much at all.

Monastics want to taste the pure, sweet milk of life, so they give up craving completely. Tanhā sours the milk. But for those lay practitioners out there, the sourness of craving can be abated by the sweetness of compassion and care. It isn't perfect, no; but then neither is the world...