add replicate image provider

[P3il4]

for now copied models list of cloudflare provider

• supports pricing formats: per run, input/output mp, per image
• follows "service:org/model" -> "org/model" + "model" alias rule
• updated docs

testing:

await puter.ai.txt2img("Turn this into a watercolor painting", { model: "flux-2-pro", 
output_megapixels: 2,
input_images: ["img url here"] })
.then(img => document.body.appendChild(img))

cost keys examples:

"replicate:black-forest-labs/flux-2-pro:run": { // per-run
    "units": 1,
    "cost": 1500000,
    "count": 1
},
"replicate:black-forest-labs/flux-2-pro:output_mp": {
    "units": 2,
    "cost": 3000000,
    "count": 1
},
"replicate:black-forest-labs/flux-2-pro:input_mp": {
    "units": 3, // input mp costs use math.ceil as during testing a 2.25MP image was billed as 3MP input
    "cost": 4500000,
    "count": 1
},
"replicate:black-forest-labs/flux-1_dot_1-pro:output": { // per-image
    "units": 1,
    "cost": 4000000,
    "count": 1
}

tested with both real key and mock server
config.json setup (under services):

"replicate": {
    "apiKey": "key"
},