This commit brings a new era to our VoIP offer by leveraging the brand new Odoo Phone Service voice cloud platform.                                                                             

Users can now buy phone numbers and configure their advanced telephony scenarios directly from Odoo.

> Young parrot looks up,
> voices ride the open air —
> someone picks up, bold.

<img width="360" height="203" alt="image" src="https://github.com/user-attachments/assets/6fa435e2-32c8-46e4-8fee-ef04e1e51de8" />

What's new
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- Buy phone numbers (DIDs) through a guided wizard: search available numbers → fulfill country-specific regulatory requirements → confirm.
- Easy user phone configuration: just assign them a DID or an extension number.
- Free internal calls through extension numbers.
- Call groups to ring several users at once.
- Call queues with agent login/logout.
- Voicemails (e-voicemails) with messages delivered into Odoo.
- Music-on-hold and reusable audio messages (uploaded files).
- Interactive Voice Responses (IVRs) with menu options backed by uploaded audio messages or TTS-generated voices.
- Schedules (business hours / exceptional periods) to route calls differently when open or closed.
- fallback destinations (no-answer / busy) pointing to any internal or external numbers.
- a visual call-flow designer.

Any DID number can be routed to a user, a call group, a queue, an IVR, a schedule, an audio message, or a voicemail.

Technical overview
------------------

Most of the work lives in the voip module, with a small install-wizard revamp in web_enterprise:

- Phone-number purchase & compliance: voip.did.number, voip.requirement.group, voip.requirement, and the voip.did.number.search.wizard.
- PBX routing layer: voip.pbx_destination_mixin, voip.extension_destination_mixin, voip.extension.
- Telephony features: voip.call.group, voip.queue (+ agents), voip.ivr, voip.voicemail (+ messages), voip.audio.message, voip.voice (TTS), voip.schedule (+ open/exceptional periods).
- Cloud integration: phone_service_api (IAP client), phone_service_event (HMAC-validated webhooks), pbx_service / pbx_client.
- Call tracking: voip.call_leg, voip.call_cost_line, voip.conversation.

Known limitations
------------------

This PR lands the first, alpha-level milestone of the new VoIP offer — numbers can be bought and real calls routed end-to-end, but a few corners are still rough and will be addressed in follow-ups:

- Call logs only cover end-user calls (no IVR, or voicemail for instance).
- No conference room PBX object.
- No number condition node in the Call Flow editor yet (branching on the caller's or the dialed number).
- Webhook handling for Call Group and Queue events still has rough edges.
- The heuristic linking billing cost lines to their `voip.call` isn't airtight yet.
- Ringing a standalone SIP client such as Linphone isn't reliable yet.

Related PRs
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IAP: https://github.com/odoo/iap-apps/pull/1370
Community: https://github.com/odoo/odoo/pull/249079

References
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Task-5214642                                                                                                                                                                                                
Task-5343969                                                                                                                                                                                                
Task-6381888                                                                                                                                                                                                
(all are parts of Task-6264142)

Co-authored-by: Mohammed Basioni <basm@odoo.com>                                                                                                                                                            
Co-authored-by: Serge Bayet <seba@odoo.com>                                                                                                                                                                 
Co-authored-by: Bruno Boi <boi@odoo.com>                                                                                                                                                                    
Co-authored-by: Mathieu Duckerts-Antoine <dam@odoo.com>                                                                                                                                                     
Helped-by: Yuchen Huang <yhu@odoo.com>                                                                                                                                                                      
Helped-by: Quentin Smetz <qsm@odoo.com>                                                                                                                                                                     
Cheered-on-by: Louis Wilcket <wil@odoo.com>