feat: add organisation-level portfolio API support

[patjlm]

Summary

Relates to #132.

Finary's backend exposes /organizations/{org_id}/… endpoints for household/family accounts. Without this, a user in a couple sees only their own accounts via /users/me/…, missing their partner's PEA, AV, PER, livrets, etc.

This PR adds minimal, additive support for the organisation-level endpoints.

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New file: finary_uapi/user_organizations.py

Seven functions covering all organisation-level data endpoints:

Function	Endpoint	Result shape
get_organization_investments	/organizations/{id}/portfolio/investments	dict (aggregated, mirrors get_portfolio_investments)
get_organization_securities	/organizations/{id}/securities	list
get_organization_cryptos	/organizations/{id}/cryptos	list
get_organization_fonds_euro	/organizations/{id}/fonds_euro	list
get_organization_real_estates	/organizations/{id}/real_estates	list
get_organization_scpis	/organizations/{id}/scpis	list
get_organization_holdings_accounts	/organizations/{id}/holdings_accounts	list

Note: get_organization_investments returns a dict (same shape as get_portfolio_investments in user_portfolio.py) because /portfolio/investments is the only available investments endpoint at the org level. All other functions return flat lists.

New helper: get_family_org_id() in user_me.py

Calls the already-existing get_user_me_organizations() and returns the ID of the first organisation with organization_type == "family", or None for single-user accounts.

CLI: --org-id option on read commands

All read commands that have an org-level equivalent now accept --org-id:

finary_uapi fonds_euro [--org-id=<org_id>]
finary_uapi investments [--org-id=<org_id>]
finary_uapi cryptos [--org-id=<org_id>]
finary_uapi securities [--org-id=<org_id>]
finary_uapi holdings_accounts [...] [--org-id=<org_id>]
finary_uapi real_estates [--org-id=<org_id>]
finary_uapi scpis [--org-id=<org_id>]

--org-id accepts either a UUID or the keyword family, which auto-resolves via get_family_org_id(). Write operations (add, update, delete) are unaffected.

New integration test: test_organizations in tests/test_get.py

• Skips cleanly (pytest.skip) when the account has no family organisation — single-user accounts are unaffected
• Asserts isinstance(result["result"], list) for all flat-list endpoints, and dict for get_organization_investments, so wrong endpoint shapes are caught immediately

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Remaining gaps (out of scope, for follow-up)

The following org-level endpoints exist and return data, but are not included here because they require pagination and filtering parameters (mirroring the complexity of their counterparts in user_portfolio.py):

Endpoint	Notes
portfolio/investments/dividends	works, returns dict
portfolio/investments/transactions	works, paginated list
portfolio/checking_accounts/transactions	works, paginated list
portfolio/credit_accounts/transactions	works

The following endpoints do not exist at the org level (404):

• portfolio/cryptos/distribution
• portfolio/crowdlendings/distribution

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Design notes

• All changes are purely additive — no existing function signatures or behaviours are modified
• The approach matches the design option discussed in Add support for Organisation #132: expose org-level functions explicitly rather than auto-switching inside existing functions. Callers opt in by using get_family_org_id() + the new get_organization_* functions, or via --org-id family on the CLI
• Single-user accounts are unaffected: get_family_org_id returns None and the new module is never imported unless explicitly used
• Validated against a real family account: get_organization_holdings_accounts returns 40 accounts, get_organization_real_estates returns 2 properties, get_organization_fonds_euro returns 6 funds, get_organization_securities returns 26 securities

Test plan

• Run existing test suite — all existing tests pass unchanged
• On an account with a family organisation: test_organizations passes with correct list/dict shapes verified
• On a single-user account: test_organizations skips cleanly
• CLI: finary_uapi holdings_accounts --org-id family returns combined household accounts