chore: release v1.5.3 with scheduling policy support

[gaius-qi]

Description

Bump workspace version to 1.5.3 and dragonfly-api to 2.3.5. Introduce a SchedulingPolicy enum (auto/always) that controls whether small downloads bypass the scheduler. auto preserves existing behaviour; always forces scheduler registration so other peers can discover the task as a parent. The policy is configurable per proxy rule, via the X-Dragonfly-Scheduling-Policy request header, and via the --scheduling-policy dfget flag.

Related Issue

Motivation and Context

Screenshots (if appropriate)

[codecov]

Codecov Report

❌ Patch coverage is 69.56522% with 21 lines in your changes missing coverage. Please review.
✅ Project coverage is 54.20%. Comparing base (b78b2be) to head (139aa23).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
dragonfly-client/src/resource/task.rs	0.00%	8 Missing ⚠️
dragonfly-client-config/src/dfdaemon.rs	76.19%	5 Missing ⚠️
dragonfly-client/src/bin/dfget/main.rs	0.00%	3 Missing ⚠️
dragonfly-client/src/proxy/header.rs	91.42%	3 Missing ⚠️
dragonfly-client/src/proxy/mod.rs	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2015      +/-   ##
==========================================
+ Coverage   54.18%   54.20%   +0.02%     
==========================================
  Files         101      101              
  Lines       27237    27305      +68     
==========================================
+ Hits        14759    14802      +43     
- Misses      12478    12503      +25     

Files with missing lines	Coverage Δ
dragonfly-client-util/src/types/redacted.rs	99.66% <ø> (ø)
dragonfly-client/src/proxy/mod.rs	0.00% <0.00%> (ø)
dragonfly-client/src/bin/dfget/main.rs	61.17% <0.00%> (-0.16%)	⬇️
dragonfly-client/src/proxy/header.rs	85.19% <91.42%> (+0.90%)	⬆️
dragonfly-client-config/src/dfdaemon.rs	91.60% <76.19%> (-0.34%)	⬇️
dragonfly-client/src/resource/task.rs	3.04% <0.00%> (-0.03%)	⬇️

... and 1 file with indirect coverage changes

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