refactor(mail): address PR #935 round-1 review

- models/mail.py: lowercase `list` generics per CLAUDE.md convention.
- client/mail.py: _ocs_get now inspects ocs.meta.statuscode (re-raises >=400
  as HTTPStatusError carrying the OCS code so callers' 404/403 handling
  applies) and guards response.json() against non-JSON bodies (RequestError).
- Extract the duplicated _format_addresses + content reconstruction into
  vector/mail_content.py, used by both processor.py and context.py (fixes the
  SonarCloud new_duplicated_lines_density gate).
- processor.py: add the missing mail_message Qdrant payload block so the
  computed mail metadata (subject/from/to/cc/date_int/has_attachments/
  account_id/mailbox_id) is actually stored, not dropped.
- Rename the list_messages `filter` param to `search_filter` (avoid shadowing
  builtins.filter); still maps to the OCS `filter` query param.
- Docstring notes: has_more heuristic, attachment content size.
- Tests: OCS meta-failure + non-JSON client paths; initial-sync scanner tests
  (tests/unit/vector/test_scanner_mail.py).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

nextcloud_mcp_server/models/mail.py

@@ -1,7 +1,5 @@
 """Pydantic models for Nextcloud Mail app responses (read-only)."""
 
-from typing import List
-
 from pydantic import BaseModel, ConfigDict, Field
 
 from .base import BaseResponse
@@ -41,7 +39,7 @@ class MailMailbox(BaseModel):
         None, alias="displayName", description="Human-readable mailbox name"
     )
     account_id: int = Field(alias="accountId", description="Parent account ID")
-    special_use: List[str] = Field(
+    special_use: list[str] = Field(
         default_factory=list,
         alias="specialUse",
         description="Special-use roles (e.g. inbox, sent, trash)",
@@ -94,10 +92,10 @@ class MailMessageSummary(BaseModel):
     date_int: int | None = Field(
         None, alias="dateInt", description="Sent date as a Unix timestamp (seconds)"
     )
-    from_: List[MailAddress] = Field(
+    from_: list[MailAddress] = Field(
         default_factory=list, alias="from", description="Sender addresses"
     )
-    to: List[MailAddress] = Field(
+    to: list[MailAddress] = Field(
         default_factory=list, description="Recipient addresses"
     )
     mailbox_id: int | None = Field(
@@ -123,14 +121,14 @@ class MailMessage(BaseModel):
     date_int: int | None = Field(
         None, alias="dateInt", description="Sent date as a Unix timestamp (seconds)"
     )
-    from_: List[MailAddress] = Field(
+    from_: list[MailAddress] = Field(
         default_factory=list, alias="from", description="Sender addresses"
     )
-    to: List[MailAddress] = Field(
+    to: list[MailAddress] = Field(
         default_factory=list, description="Recipient addresses"
     )
-    cc: List[MailAddress] = Field(default_factory=list, description="CC addresses")
-    bcc: List[MailAddress] = Field(default_factory=list, description="BCC addresses")
+    cc: list[MailAddress] = Field(default_factory=list, description="CC addresses")
+    bcc: list[MailAddress] = Field(default_factory=list, description="BCC addresses")
     has_html_body: bool = Field(
         False, alias="hasHtmlBody", description="Whether the body is HTML"
     )
@@ -138,7 +136,7 @@ class MailMessage(BaseModel):
         None,
         description="Rendered body (sanitized HTML if hasHtmlBody, else plain text)",
     )
-    attachments: List[MailAttachment] = Field(
+    attachments: list[MailAttachment] = Field(
         default_factory=list, description="Message attachments"
     )
 
@@ -149,21 +147,21 @@ class MailMessage(BaseModel):
 class ListAccountsResponse(BaseResponse):
     """Response model for listing mail accounts."""
 
-    results: List[MailAccount] = Field(description="List of mail accounts")
+    results: list[MailAccount] = Field(description="List of mail accounts")
     total_count: int = Field(description="Total number of accounts")
 
 
 class ListMailboxesResponse(BaseResponse):
     """Response model for listing mailboxes."""
 
-    results: List[MailMailbox] = Field(description="List of mailboxes")
+    results: list[MailMailbox] = Field(description="List of mailboxes")
     total_count: int = Field(description="Total number of mailboxes")
 
 
 class ListMessagesResponse(BaseResponse):
     """Response model for listing message envelopes."""
 
-    results: List[MailMessageSummary] = Field(description="List of message summaries")
+    results: list[MailMessageSummary] = Field(description="List of message summaries")
     total_count: int = Field(description="Number of messages returned")
     has_more: bool = Field(False, description="Whether more messages may exist")